I wish they'd include schematics on those or which pins are what but anyway just by looking at it I would guess the 2 pins on the left are the ones that are going to be connected to the 9 volt source. In series with that on the positive side of your 9 volt supply would be where your float switch will be connected. The 3 pins on the right would be where the ac voltage would go. One pin would be normally open (NO), which means it is not powered when the relay is not activated, one is normally closed (NC) and one is common (C). Connect one of the wires on your AC plug to the outlet where you are going to connect the ATO to and the other wire to the NO pin and the C pin goes to the Outlet. Not sure which is NO, NC, or C from the 3 pins. I guess you have to test out which if no diagram is given.
http://www.embed4u.com/?p=380
there's a schematic there, which shows a better way of wiring it.