Cut the old plug off the cord with the wire cutters.
Strip off 1/4 inch to 1/2 inch of the outer cable jacket. Do not strip any of the insulation from the inner red and green wires. If the outer cable jacket is cloth, push it down the cable or cut it with a pair of scissors.
Hold the RJ-11 plug in one hand with the locking tab facing down and the metal contacts, or pins, facing away from you. Pin position No. 1 is on the left; pin position No. 6 is on the right. Most RJ-11 plugs will not have copper contacts in positions one or six.
Push the red and green wires into the center of the RJ-11 plug. Make sure the red wire is over contact three and the green wire over contact four (the center two contacts).
Crimp the RJ-11 plug down on the wire using the crimping tool. The plug is designed to pierce the insulation and make contact with the copper wire.
Plug the phone into your wall jack and test it by making a call.