Use a hammer to gently remove the knockout hole located on the side of the boxed outlet through which the BX cable will run. Do not use much force or you may break or damage a part of the box or the wall.
Twist the metal sheath in the opposite direction of the natural twisting of the visible grooves in order to break it. Use a cable cutter or saw to cut through the cables. Twist the metal sheath again about eight inches from the end of the cable to break it, leaving the cables exposed. This will allow you to move them around and connect them within the box.
Trim away the insulation and cover from about half an inch of the exposed cables to see the actual wiring inside the BX cable. Push the cables through the anti-short bushing so that they will be protected from the metal sides of the sheathing or the outlet box. Snap the back of the bonding strip back on the anti-short bushing to lock the cables into place.
Attach the BX cable to the outlet box with a BX cable connector. Secure the connection with a clamp as you attach the cables. The cables are color coded, and the color of the insulation on the BX cable matches the cables coming out of the outlet box. Use these colors to create pairs, and connect all of them one by one. The bonding strip is installed based on the electrical codes in your local area. Check with your city or a licensed electrician for the proper procedure.
Secure the cables within the outlet box, and close the box to complete the installation.