How do i gain friends? ?

I'm really shy. Have maybe 3 good friends (at least I think) I don't have many peoples numbers but I would like to talk to more people. I've gone to school with the same people for about 7 years and don't talk to most of them. What can I say to be there friend and it not be weird? If it helps I was in a controlling relationship for 2 year and got out 3 months ago. I gave up all my friends cuz of him. Please help :(