Step 1: Pick up the magazine catch.
Step 2: Insert the magazine catch into the lower receiver, on the left side.
Step 3: Pick up the magazine catch spring.
Step 4: Insert the magazine catch spring into the receiver, on the right side, over the magazine catch post.
Step 5: Grab the magazine catch button.
Step 6: While holding the magazine catch, screw the magazine catch button onto the post. Screw it down as far as you can with out scratching your lower’s finish.
Step 7: Grab a tool to depress the magazine catch. In this instruction, I used a house key. You can use a small screwdriver, a ball point pen from the bank or an old toothbrush. Anything that you can use to push in and hold the button. Step 8: While depressing the magazine catch button as far as you can, you will screw the catch in until it seats fully in the receiver. You will need to turn it clockwise, or as in the orientation in this picture, towards yourself.
Step 9: Check your magazine release button. See if it operates properly, and check to make sure the catch post does not extend past the button. If it does, depress the button with your tool and back the catch out a turn or two.
Step 10: You are done!