Shampoo-er

Question

This seems to be a common problem, the shampooer is putting out alot of water and hardly any suds. I read through the posts about the little filter that sometimes gets out of place and I think I found it in the box - is it about 1" diameter hard plastic ring around very fine mesh? If so where exactly does it go? Some posts say in the hose, and others say in the opening of the tank. Or does it go in the place where the hose attaches to the tray? I also found a round sponge in the box of shampoo stuff - it about 2" diameter and 1/2 " thick. Where does that go?
The manual doesn't even mention the filter or sponge.