From the photo, it looks to be a simple Venturi driven skimmer (like a seaclone only larger).
You water level will be regulated by the large pipe to the left. If it's not adjustable, then you have a static water level. The level in your sump will also play a role. The skimmer will have a certain level that it needs to sit in in order for it to work well. You'll also need to have the water level a constant (no fluctuation).
Make sure there is no obstruction in the airline, also.
Other than that, wait for it to break in.
How long has your tank been set up?