Cat5e cables are the industry standard for all types of network connections, even replacing standard flat phone cables for use with RJ12 connectors. Of the eight wires contained in a Cat5e cable, RJ12 connectors use only the six wires required to transmit voice and data, so you must know which wires to use before beginning the RJ12 connector installation. Once you know what wires to use, however, installing an RJ12 connector on a Cat5e cable is the same as installing a standard flat phone cable.
Strip off 2 inches of the Cat5e cable's outer jacket. Untwist the four pairs of wires contained within the cable and straighten them out. Cut the brown and brown-striped wires as close to the cable jacket as possible; they will not be used with the RJ12 connector.
Place the remaining wires in the following order from left to right: green-striped, orange-striped, blue, blue-striped, orange, green. Put the wires together so that each wire is touching the one next to it. Strip 1 inch of each wire's jacket away from the wire.
Hold the RJ12 connector with the clip facing down and slide the connector over the wires. The green-striped wire should go into the pin that is the farthest to the left, followed by the orange-striped, the blue, the blue-striped and the orange. End with the green wire being inserted into the pin that is the farthest to the right.
Insert the RJ12 connector into the crimping tool and crimp the connector down to lock the wires in place.