How do i ask out i boy i like ?

i like a guy named dawson i want to tell him yet i cant get the right words i fell for him when we were in 6th grade he was sooo nice and then he and i spent alot of embaressing times together like one time a girl name yani through a paper at me ( we were having a paper war ) but i stopped playing to listen to the teach and she through it it landed in my shirt RIGHT THERE!! he was watching and he laughed i was blushing like crazy!!! i rly didnt know that it had gone down my shirt till i noticed they were laughing and asked whats up!! plz gimme advice!! thx