The capitol has a large free parking lot on the North east side of the building, that is well equiped to handle large events like this.
Note from a UTA fan:
I strongly suggest you let those wishing to attend know that they can get a ride to the capitol on UTA route, 461, 463, 470, and 500. Route 500 starts at the North Temple Front Runner station. and so a round trip fare on the Front Runner from their closest location would be a far better choice than trying to find parking at the capitol on the 18th.
Anyone can go to rideutah.com to get the route information they need.
If they go the that website and click on "Trip Planner" they can get the local station times for these routes going past the capitol, and associated transfer possibilities from Front Runner or Trax stations or other bus routes.