How do I forgive someone?

So recently I was looking at the story of joesph and it really made me feel like I had to forgive this girl. A few weeks ago she basically played me and kind of broke my heart. I'm not speaking to her right now and everytime I think of her I get feelings of anger and sadness. When it first happened I took pills to try and get high off them to forget about her. I'm not a druggie and have never done anything of the like before. I don't even know why I did it. After the incident happened she tried to give me a hug and say she was sorry but I blew her off. This was the second time she did this. Anyway I want to forgive her though now, but how? I don't really know how exactly you forgive someone. Should I talk to her about it? Right now I really can't see myself saying a word to her. So my question is, how do I forgive?