The valve on the side panel is the fill and empty valve. It controls the live well flapper valve in the sump with the pump mounted on it.
Turn it past the little detent to hold water, and it fill while recirculating about 40%. When in like new condition.
The valves on the rear of your livewells turn off and on to flush the spray bars of debris from crawfish and such. The small 1/8″ holes can become clogged with grass and matter. So when that happens, press the debris back into the spray bar with a probe, and flush the gook out the ball valves into the sump and drain it out the drain tube.
There should be four pumps on most. One controls the livewell aeration, one controls the recirculator. The other two on the sdie panel are optional and only if you have the pro-aeration feature.
If so, then one is fresh water in without timer or regulation. The other is for culling and weigh in to get the fish out easily and is a pump out.
You should also have a manual for your dash if this is a BP dash model of the P2. You will have a BP-101 unit.
Hope this helps!
BCB