Ok, my crush broke up with his girlfriend?!?!?

i really like this boy named dennis and he broke up with his grilfriend destiny. i really liked him but i took long to tell him. so they broke up yesterday and i feel really sorry for him. (destiny is my friend also) so i ended up hooking them up and it may seem bad but i regret it because i really wanted to be with him. so anyway, when should i tell him that i like him and how do i tell him i really like him???. me and him play around alot. he pokes me alot too but i really like him and i wanna know how and when do i tell him?