Measure and mark the area in which your racks will sit. Mark the corners and other locations along the bottom of the rack that will be bolted to the ground.
Drill holes into the ground with a hammer drill in the marked locations. There is typically a bolt at each one of the rack's legs, which contain a mounting plate with bolt holes.
Place the base of the rack over the marked and drilled areas. Align the holes in the ground with the holes in the mounting plates.
Insert anchor bolts through each of the holes in the mounting plates and into the ground.
Secure the bolts to the mounting plates and the ground by tapping them with a hammer until they won't go any further. Turn each bolt clockwise with an adjustable wrench until the head of each bolt sits on the top of the each mounting plate.