The first thing is to gather your parts and tools. Durr!
Here, we are going to use a Power Drill and various bits, Soldering Iron, Heat Gun (or lighter if you don't have one), Wire Cutters, Hemostats (surgical clamp. well worth getting some), Screwdrivers - Standard and Philips head, a Nail or some other sharp pointy thing to mark the box for drilling holes, and last but not least, Pointy Nose Pliers.
I think that is all the tools, other than myself! that I need.
First off, I started by disassembling the Safety Switch. This allowed me to get the correct size for the hole we are going to drill to fit it, and to position the switch on the box, in the most central position.
Here you can see I used the yellow face plate to best find the layout. Putting it in closest to the centre of the box will give the switch the most stable position when using this device.
Getting it close to centre visually is good enough here