How do you flirt?

I’m new with guys and stuff so I want to know how to flirt and stuff and I want to know what to do when they do something .. and im in 8th grade incase that helps …

I sit next to this guy in science and my friend is an expert flirter and everything but I feel weird asking her.. or my other friend.. whos not an expert.. but she knows how and I have to clue what to do because if I like him and I do talk to him im not sure how to.. add to it .. we’ve hung out once at the movies.. and I didnt know what to do .. he had my phone and was texting my friend on the phone .. and he was messing with her and I didnt know how to flirt or anything and when its me and him alone, its different and I feel a different thing between us and then when were with my other friend and her boyfriend its different and I don’t know what to do and I don’t know how to flirt or try to get him to like me !! please help !!

also another thing .. if were in science apparently according to my friend is im wearing a sweatshirt or whatever and he like reaches in my pocket or starts playing with my pocket what am I supposed to do? I know this might sound desparete but I am and I need help !!