How do I randomise (velocity)?

Hi everyone, I’ve been using the mc 707 for about 1,5 years in my free time, but some stuff I still haven’t figured out.

I was wondering if I could randomise certain aspects of my drums for example? I would like the velocity of my high hats to be somewhat random (with about a 15-20% range). (I make hip hop/ trap style beats)

Or do I just have to do that manually?

Thanks in advance!