When you go to the track page for this event, open the pre-register, and it should show a matrix and wrestler list. quick check with matrix or look up competition with wrestler list. You may have to keep tabbing forward until you get to the right age/class.

There are a lot of people who enter last minute so keep an eye out. From experience once some one enters a group that didn't have anyone in it, then it fills up quickly. It's a strategy I guess...