whats my first step if i can not afford a lawyer?

I sold to an undercover cop through a "friend" that had asked me to meet him for one ounce of weed. I went home that night as if nothing happened. a month later I came to meet up with the same guy and was arrested before I could even make another hand to hand transaction. the person I sold to was an undercover like I already said. they have me now and want me to work with them in order to drop or significantly reduce my charges. the thing is, I don't want to be a snitch. so I want to know what I should do since I cant afford a lawyer. the first sale was back in november 2014, then in December 2014 I was busted. they decided to do a round up and call me this past 4th of july 2015. I'm broke and don't know what to do.