How to talk to this guy i like??

ok.so im sorta shy with guys idk.and the guy i like is doing summer gym cl for high school w me.he went to the public middle school where as i went to a catholic middle school.he already knows ppl cuz he went to that school and i dont know a lot of ppl.i really like this guy cuz he isnt like perverted or anything and hes super nice.idk what to talk w him about cuz we didnt go to the same school or anything.i have his sn from a friend.show i talk to him without him knowing my sn?or what should i do?what are some things that i can start a convo w him??