It might help if you could find a picture of it or post one here, so that folks can help you identify it.
Generally, the procedure is as follows:
Check that the holding tank
Check that the Y valve that lets you choose between holding tank
is set to send waste to the holding tank.
Open the seacock that feeds raw water
to the toilet.
Flip a lever on the toilet that allows raw water
to come in.
Flip the lever back to the dry position.
Pump until the bowl is empty.