It's not just the directions, the unit is crap. Dont' expect any decent results or anything. The collection cup has to be out of the water. The little slits in the side , where water returns to the tank, has to be out of the water, or at least at the surface. These units are severely prone to adding lot's of microbubbles to the system whenever it's running. And it'll stop skimming altogether if water level is not stable. Any decrease and you see a massive decrease in effectiveness of the unit that wasn't very good to begin with.
I threw mine in the garbage...literally. and kept the small pump for nano uses.