You need to unlearn the kinds of behaviours you engage in that predispose you to bullying and social exclusion. You need to give yourself a chance to learn the things you weren't able to through your childhood and teen years. There really is no short-cut when it comes to learning social skills, it means going out and interacting with other people.

If you live in a big place this is easier but..
-make conversation with people while waiting for bus/train etc say ask for the time or chat about the weather
-go into stores and ask whether they have X thing in stock, -chat with the hair dresser when they do your hair.
As you improve you will find it easier to talk with people in general, you will learn some basic 'social scripts' that everyone uses to get by with social interactions.

Practice as much as you can before you go to community college to give yourself the best start you can. You have to expect some minor embarrassment and nerves while you practice improving yourself, but in order to improve it is necessary to forget and keep trying.

My general advice is to basically pick someone who manages to get by socially and try to emulate their behaviour (within reason). Watch how others engage in small talk and follow their lead, watch their general interactions and most of all be interested in what people have to say.