It's really sort of simple, it's just not easy. One loves another person, gender doesn't matter, by accepting them as who they are.
Let's say for the sake of this discussion that there are three categories of things one is challenged to accept about any other person. First are the things one prefers. These are the things one is drawn to in the other, it may be their physical beauty, their wit, their empathy, their knowledge, their judgment, their background, whatever. These things are not the problem. We lean towards these things, they are usually the reasons that people give when reciting "this is why I love thee." The popular theory of love relationships is that we mate-up with people who have so many of these qualities that they sustain our desire to persist in the relationship when experiencing the other two categories. In the early part of a romance, the "in-love" part, these may be the only things one sees (or acknowledges as real) in the other person.
The second category contains things one is neutral about. These are the facts of the other person's life that don't really attract or repel at all. It may be their geographic origin, their preference of pain reliever, the way they fold laundry, their hobbies, their favorite sports team, whatever, it is just the category of stuff that has no weight emotionally. If one is "in-love," one may find these things interesting because one is gobbling up knowledge about the other, but really one is just filing this stuff away as bits of information, they don't change the mind either way about the dedication one wants to make to the other.
The third category contains the things that repel one about the other. Emotionally immature people, or those too deeply "in-love" to really see anything, will deny they exist, or they will minimize their number or importance with denial and willful ignorance. These things are where the work is. These things generally determine one's willingness to remain in the relationship, they confer boundaries to intimacy, and they are the keys to really being with another person.
It is with these things that one must work in order to love another person. That's right, that is what loving another is all about.
One may seem to have a choice here, but it's a straw-man choice. That is, one may think that one can either bring about a change in the other which eliminates or mitigates the repugnant quality or that one can change themselves to accept these repugnant qualities in the other.
If your experience is like mine, you've had enough trouble with changing something about yourself even though you really do have almost total power over that process. Imagine then the success one should expect to enjoy with changing something in someone else, where your power is non-existent.
So, there's no choice there. If you want to know how to love someone, the task is really straightforward, you have to accept what repels you about them. That's a really liberating realization when one finally reaches it. There's nothing that the other person has to do. This is completely under one's own control.
It also has nothing to do with having sex with them. I used to wonder what it meant to love another man. This is it. When you pare it down to these essentials, this is really the difference between a preference for another and loving another.
This is also a separate issue from intimacy. Love and intimacy go together, in fact intimacy depends upon loving and being loved as I define it here, but intimacy requires a mutual commitment to this process of handling one's own aversions regarding the other whereas love does not.
People I've seen go through a series of marriages, or serial commitments of equal magnitude, who come to believe that they kept picking the same kind of person over and over again, or that they had the same time of relationship over and over again, or that marriage is always this and husbands always do that, are really just seeing themselves in the mirror and marvelling at how the image is always the same.
The only way to really change one's experience of any relationship is to work on accepting the things that repel one about the other person. How does one do that?
First, it is very important to discern the difference between acceptance and approval. Acceptance is about detaching yourself from your own thoughts. For example, consider that I finding it highly irritating when another person drinks bottled water in New York City. We have the best municipal water supply in the world, so clean that filtering it does not improve it, and drinking bottled water means that one is wasting the resources required to manufacture the bottle, transport it, stock it, chill it, sell it, use it for 20 minutes and then dispose of it for tens of thousands of years, or to power the recycling apparatus that turns it into something else. I have a hard time thinking of something more thoughtless and selfish done for so little gain.
Those are all thoughts of mine. I have a right to them, I think I'm correct, but they are not real.
I used to buy bottled water by the case and drink it almost exclusively. What happened to my reality then? My thoughts then about how bottled water made me drink more of it and less of other less-healthy alternatives were just as persuasive. I believed that as adamantly as I believe what I do now.
Everything changes, particularly thoughts, so why have such respect for them? Drinking that bottled water may have made it possible for me to survive to reach the understanding that bottled water is a public menace and become the evangelist I am now for not abusing our landfills (or recycling infrastructure) with water bottles.
So, why should thoughts like that stand in the way of loving another person?
Approval is different. I do not have to approve of something in order to accept it. I simply have to realize that my thoughts are not reality. There's more under heaven and earth than can be explained by my philosophy.
Acceptance doesn't mean martyrdom. That doesn't mean I have to not take care of myself. I may have to figure out a way to co-exist with something that repels me in my loved one. If they insist on spending money mindlessly I may have to construct a personal financial model/method that protects my financial well-being from this. If another insists on being sexually unfaithful I may have to end the sexual partnership, and that may cost me the rest of the relationship, but it need not require that I stop loving them (I have, in fact, done this very thing. I broke up with her 20 years ago but I still love her as I did when we were engaged).
So, this is why love can be so confusing, I think. People use the word to describe too much. Love is the consequence of radical acceptance. You love someone when you honor them as being perfect as they are, in spite of your preferences, in spite of your disapproval, you accept that this is who they are and you regard them positively anyway. Your breaking free of the shackles of your own thoughts, of convention, of prejudice and of judgment.
It is at this point that love transcends attraction/repulsion and actually becomes a religious experience. This is when it causes us to come into contact with something that connects us all--the essence of the religious experience.
That's how you love someone.