The original relay will have 2 large and 1 or 2 small wires. A large wire will go from battery+ to one large terminal on the relay and another large wire from the other terminal on the relay to the starter. You need to have one large wire from battery+ to the large terminal on the starter. If you want to use the existing wires just put both large wires on the existing relay on one terminal. You are just using the relay to connect the 2 large wires together.
If there is 1 small wire on the existing solenoid it just needs to be connected to the small terminal on the new starter solenoid. This wire is what energizes the starter sole oid whe the key is turned to start. If there is a second small wire on the existing relay it is a ground wire. If both small wires disappear into a wire bundle you just need to figure out which one gets 12 volts on it when you turn the key to start.
