Symptoms of a bad starter solenoid are a starter that stays on after engine is started or a clicking sound when you turn the key to try and start the vehicle.
A bad starter solenoid can make a clicking sound but it can also be the battery that is low or has bad connections so check the battery first to make sure the battery is fully charged and the connections are clean and tight.
If the battery is good and the connections to the battery are good and the starter solenoid still clicks when you turn the key then either the solenoid itself is bad or the starter is also bad.
Since you have to remove the starter anyway to change the solenoid it's best to just replace the whole starter and solenoid together.