Well, the upside is that on the internet, physical appearance, skill, and health do not matter at all. What matters is what's between your ears, and how you use it. It has the double-edged sword of anonymity - no-one knows who you are, there are no pre-conceived notions about you, and whatever people say - you can always just log off and leave. It also encourages people to act like twats because they too, can simply log off and leave without any repercussions.
My advice would simply be to say hello to people. Presumably there's a forum or chat of some sort to keep in contact - so start a topic about gaming. Either your favourite game, or just in general. Odds are you'll find a few people to talk to quite swiftly, since pretty much everyone and their dog plays games these days. In the stupendously unlikely case that you can't find any gamers amongst your schoolmates, you can always look for other people who do game. The beauty of the world is that it's filled with an endless supply of people, and there'll always be a few out there who like you.
Depending on the kind of games you enjoy playing, it should be relatively easy to join in a related community. If it's a single player game, look up forums, chat rooms, modding communities or whatnot and hang around there. If it's a multiplayer game, look up a guild/clan/alliance/corporation or whatever it's called in your game of choice. Simply start with a hi. Offer to help people, give advice, explain things or possibly start tinkering around with mods. Just talk about the game, or game related things. People will talk back. Move on to different things when you feel comfortable enough with said people. Repeat until friends.
I realise I'm making it sound a lot simpler than it might seem - but that really is it. You get better at making friends by making new friends. You get better at talking to people by talking to people. Experience is the way to go in these cases.