Step 1: Locate the two Phillips-head screws pictured below.
Step 2: Gently remove the two grip pieces from the side of the stock, as shown below.
Step 3: Line up the stock with the body of the gun and slide the stock onto the body piece as shown below.
Step 4: Insert the screws in the correct holes, with the long screw on top and the short screw on bottom. Do not fully tighten the two screws until you have them both started.
Step 5: Snap the grip pieces back on and its ready to go.