You can jump the center post (12v supply) to either the left or right post to activate the motor. Which post is forward or reverse will be quickly apparent.
On Edit: Don't try this!! Based on Post #6 below, you may let the smoke out. You can jump from the center post to a spade connector but if the solenoid is not working this likely won't work either.
You say you are waiting for the part. Here is one you can have tomorrow.
https://www.amazon.com/Trombetta-214...00089224&psc=1