All the parts for the Base are laid out in the photograph.
Circuit board, two M3 nuts and screws, four plastic rivets, one servo and the case.
Place the servo in the cut-out in the case, note that the hole is offset, see the picture for the correct orientation of the servo. Place the plastic rivets in the holes and push down on the top of each rivet until they are closed.
Plug the servo lead onto the header on the circuit board. Make sure the black lead is nearest the regulator as shown.
Place the case over the circuit board, make sure the servo lead is not trapped and then fasten down the case using the M3 nuts and screws. You will have to peel back the foam rubber backing to put the screws in position, then tighten the nuts and screws using a small screwdriver, stop the nut turning by pressing on it with your finger.