First would be checking to see if you are getting 12 volts to the solenoid to energize the the two large post on the solenoid. Most likely you have two small wires on the solenoid, one will be grounded to the engine block and the other should have 12 volts on the harness side when turning the key to the start position. If you do not get 12 volts when turning the key to start position then the issue is on the harness or key switch. if that checks out fine then you can jump the two large wires on the solenoid to see if the engine turns over which means the starter is not the issue. If the starter turns and sounds strong then you would be replacing the solenoid. Here is a link to the parts diagrams.