In the bilge of your boat, you'll see a thruhull in the hull bottom, that is your livewell pickup. Attached to the pickup will be a shutoff valve with a yellow handle. Now, there maybe a pump located on top of that shutoff valve, there may be a hose running to a pump. Yhat is your livewell pump. From the pump, a hose will run to your aerator head.
Valve open, turn on the pump at your helm, livewell fills. Turn off the pump. On a boat as small as yours, there will probably what's called a "stand pipe" which inserts in the drain and has an open top with a strainer on it. That way, if you leave the pump on, once the water level reaches that strainer, it will start to drain the livewell. Want to drain the livewell now? Simply pull the standpipe out.
It's as simple as that...