Assuming you have the backstop and the tires, you will need to do the following:
1. Place the backstop in the desired location.
2. Unpack the tires and place them around the base of the backstop.
3. Once all four tires are in place, begin screwing in each lug nut by hand until it is tight. Be sure not to over-tighten as this can strip the threads.
4. Using a wrench, finish tightening each lug nut until it is snug against the tire. You may need to use a tire iron for extra leverage.
5. Repeat on all four tires until they are all securely fastened to the backstop base.