There are 2 bearings on each side. Remove the big lock nut first, then wiggle the caliper to see if the outside bearing comes out. You have to remove the rotor to get to the inside bearing. It will probably have to be tapped out(carefully) with a flat nosed punch and hammer. Make sure the spindle isn't worn. Pack the bearings with bearing grease and replace. Tighten the lock nut enough to remove all slack, but where it still rotates freely.