Put a jumper cable on the positive battery terminal and the other end temporarily touch it to the large post of the starter.
The engine should turn over, if not, then you know the problem is the starter.
if it does turn over then the problem is in the associated electrical circuit.
CAUTION:
You can get a large spark while touching the jumper to the starter lug and be prepared that the engine could start, so make sure it is in neutral, and you are in a safe situation, as you are circumventing all safety devices.
Best to unload your parts cannon and do more diagnostics
