The purpose of the Placement Test is to see how much you know by heart already. Therefore they actually recommend you NOT to revise for anything
So you don't need to worry about revising anything.
After the Placement Test, you will know your result on the same day. For example, if they put you into Level 3 and you find it too hard/easy during your first few weeks of classes, then you can request to move to a higher/lower level.
However, the result from your Placement Test might not be very accurate since they are only testing on a small area of knowledge. So after you know your suggested level, go to the library or the bookshop and have a browse through that level's textbook. If you know most of the stuff from that textbook already, I would suggest you try a level higher.