Well first off, I would start by breaking down any gender-specific rules you might have stuck in your head. You can do this BEFORE going out and trying to conquer your fear, and it'll prep you in a more important way then you can imagine.
Now, I'm not saying that you're some terrible stereotyper, but psychologically speaking, (and anthropologically speaking) everyone has traits that they attribute to certain people; things that they unknowing, naturally assume about, say, men.
Some are true, many are not, but the key for YOU here is that you're trying to overcome a fear of them. So, I suggest taking some time to sit and think about your idea of a man. What do men DO? What do you think they THINK ABOUT? What do they wear, were do they hang out, etc.
For this sort of problem, it doesn't really matter if your answers are stereotyped, because eventually as you become less afraid of men, you'll start hanging out with them more. *But stay with me here, I know it's a long text.*
Your answers might be, for a very stereotyped example, men play video games, drink beer, watch porn, and play football. They like to wear really comfy clothes, like athletic shorts and tanktops/beaters. They hang out at arcades, bars, and their buddy's houses.
OK, now, based on your answers, ask yourself what parts are scary or uncomfortable for you. Then, even MORE important, ask yourself if any of it seems like something you do.
"Well, I really like video games, and comfy clothes, and I spend 76% of my time on the internet looking up hentai." (Jk, just an example~)
This may help you see men as more just plain people, as opposed to this foreign concept that frightens you. You might feel better knowing there's a little bit of "man" in your own personality, making it easier to then go out and say, make one male friend. (: