Set the DC to 3-5. Turn the large white dial to "bottom out" the water. Adjust the air to make a nice foam. Turn the large white dial to raise the water level/ foam/ collection rate. Then just tweak the air to get a good froth.
Higher bioload, go to a higher DC pump number. If it looks like boiling water, dial back the air. If the skimmate looks watery, turn the big white dial down.
In the begining it is just going to bubble as it is breaking in.
One tip, make sure the screw that holds the orange gear to the big white dial post is tight. It was slipping on mine, but after tightening worked great.