Did you receive an owner's manual with your rake? It has installation instructions and pictures for the wheel kit. All the pictures in my manual show two wheels. It looks like the wheel mounting brackets use the tine attachment bolts. If you don't have a manual go to the Howse web site or call them at 601-428-0841.
They mount using longer bolts(provided, I think) through the same holes that mount the tines. You mount them inboard enough so that when the rake is angled, the wheels stay within its footprint.