How to fix timing of recorded audio beat with hitpoints

Hi, I haven’t used cubase in a while and I don’t remember how to do this. I recorded some hand drumming and want to fix the timing. I also would like to focus on only a part of the audio file so I can just use that 4-bar section over and over once the shakers are hitting their 16s.

I opened the audio in Sample Editor and clicked on Hitpoints. Now how do I make sure they hit on 16s like they’re supposed to? And also crop it to just those 4 bars.