It is a fairly simple system. The toilet brings in raw water from a seacock. It then grinds up the waste and moves it to a holding tank. When the tank gets close to full, you go to a marina that has a pump out station and have them empty it. My marina charges $4. There is an access cap (mine is on the port side) that they use to pump out.
To make sure the toilet is working, first find the seacock for the head and make sure it is open so that the pump can draw water. Then find the holding tank and make sure it isn't full. There is also a Y valve at or near the holding tank that allows you to pump waste overboard. Make sure the valve is set to send the waste to the tank. And if it isn't already, remove the handle from the tank or otherwise secure it so no one moves it to overboard discharge by mistake.
Next, push the flush and hold the flush button. You should hear the pump and see water dump into the bowl. Add a little holding tank treatment (most boat supply stores carry it). You are ready to go. After you use the toilet, hold the flush button down until all the waste is gone, plus a couple seconds. Only use marine rated TP. Hope that helps.