How do I set my GPS receiver to use UTM?

You will want to go into the setup menus for your GPS and look for menus like "Navigation" and "Position Format". You should find a menu that gives you choices like:

MGRS

UTM/UPS

USER UTM GRID

hdd.ddddd

hddd mm.mmm

hddd mm ss.s

You want to select UTM/UPS.