I'm not looking at mine, so I don't know where that (1) screw is, but in case you didn't look, are there any screws inside the battery compartment ?? Or is that where the (1) is at ??
I'm guessing it's the typical thing you have to pry apart really, really carefully. Without knowing where "tabs" are and what-not, you're bound to break one or more and then it won't close properly....
Remove batteries and the one screw. Insert a flat screwdriver in one of the screwdriver-size slots on either side near the back. Carefully work the blade into the groove between the top and bottom parts, then slowly slide the blade all the way down the groove to the other end. Repeat on the other side. There are five little clasps on each side that will "pop" as you do this.
Be careful pulling it apart. Make sure not to lose the little piece attached to the tiny switch above the battery compartment (UHF Pro only)