Two bolts were used to mount it, using one of the bolts to connect the ground wire that is wired to the ground on the engine. This is the wire that goes up the wire harness to the glow plug switch. DO NOT cut the end off the wire to make it shorter. If you ever have a problem with the solenoid, then you can connect the system back the way it was. Connect this white wire to the small stud on the solenoid.
Some solenoids have two small studs.
One is not used. Before installing, ground the solenoid and touch a hot wire to the small studs one at a time. That is the one you connect the white wire to. Hold for 25 sec, shut key off and return to engine and see if you can burn your finger on the top of a glow plug. It still should feel hot.