Measure the camper shell. Ensure the shell is the same measurement as the truck bed. Lower the tailgate. The extra room will be needed. Lift the camper shell on the bed. Make sure the shell lines up with the truck bed. No part of the shell is overlapping the bed. You may need a partner to help you lift the camper on the bed and align it properly.
Clamp the flat edge of the shell to the top portion of the bed. The top portion of the bed will have a lip where the C-clamp will tighten the shell to the pick-up bed. You can also tap holes and bolt the shell in place. The C-clamp is preferable if you desire to remove the shell on a continuous basis.
Clamp 5 additional C-clamps to the bed, holding the shell in place. You will want to ensure you have 6 C-clamps, covering the 4 corners and 2 sides. This will prevent the shell from ever slipping off.
Torque all the clamps down snug. You can tighten the clamps with a pair of pliers to ensure it is tight. Raise your tailgate. You can test the rigidity of the shell by pushing on it to ensure it does not move when you apply force to it.