That's what I had to assume.
I've done some similar things with an Omron relay from mouser.com (about $6, just soldered wires onto the terminals).
This should help:
Motor output from switch goes to terminal labeled Motor, normally-closed side of circuit labeled Rinse goes to rinse solenoid.
Soap output from switch goes to hot of relay coil (labeled
Soap). Right now when your rinse is selected and you're rinsing with hot water, only the motor starter is energized. The same power is shunted through the relay to energize the rinse solenoid, and when
soap is selected the relay is energized and the circuit to the rinse solenoid is broken.