My finger is pointing at the wire that gets plugged into the wall. You can hook these up to be supplied by 110v or 220v. This really is the only tricky part. Mine did come with a diagram. For 110v, attach inputs on #1 and #3. Your outputs will be on #2 and #4. In my case I am using 2 bulbs so I hooked up two wires to each output. You will only be using one bulb so one wire to each output.
I'm not sure these things are all the same so be sure to get one with a diagram.