Hey there! I'm happy to help!
I will assume that you are talking in the present tense (He gets up very early).
When conjugating reflexive verbs (ones with -se on the end) to he, she, it, you formal, they, and you plural, we put the se first and then we conjugate the verb without the se on the end and we put it after.
If you conjugate despertar to he, you get despierta. The e from despertar splits because it is accented, giving us ie. Don't forget the se, we now say "se despierta" as the conjugation.
So, the answer is Él se despierta muy tarde.
I hope that this helps!
