You have to kind of put the seat material inside the ring of the swivel seat thingy, the fold it over the rim, then there should be some little button/hook/nib thingys underneath to attach the material firmly to the plastic swivel ring thingy. Then you have to sit the ring thingy (with the material seat bit now attached) on the hole of the actual station base bit. Then get under it like a mechanic gets under a car - and thump it into place!
There are 4 kind of nibby / lippy / catchy bits that you have to fix the ring bit into to keep it firm. OH found that you had to give it a good firm whack from above to get them caught in, but had to get underneath it to see where to whack. I guess you could turn the whole thing on its side... that might be easier!
