It will probably take several days to a week for the skimmer to "break in". They don't start working immediately. For the next several days, don't worry about collecting stuff or if it's too watery or too thick, etc. Just let it run. :) After a few days, you want to adjust it so that it's high enough that it's not collecting clear, runny water, but low enough that it's collecting a thicker, gunkier foam. It will take some tweaking with to get it at the right level, but that's a good skimmer and it's very user friendly once it breaks in. Good luck!
PS -- if you use any tap water conditioner, additives or chemicals in your water, that can throw the skimmer out of whack for a bit and cause it to overflow, so use caution if you put anything like that in the water.
