Wiring Options and how to install the switch:

One of the best features of this switch is its simplicity: only two wires get into your system. The white wire goes to the ground of any pot. The red wire is connected to the hot output of the output jack. That's it! No mess, no extra wires, no floating choke or inductor. Ever see the Gibson inductor? It looks like a half pack of cigarettes.

Output Jack
When you get your switch it will look like this:

Varitone Switch
Where to install the switch?

The switch can replace a tone pot in Strat-type guitars. I never understood why strats have that extra useless knob; I never use it on my strats, so I replace it with a varitone. Just wire the tone control in parallel, along with the switch. If you have a guitar full of mods already and you need to add a switch, here is an option I just did for a customer on his Tele:

Telecaster install, part 1 Telecaster install, part 2 Telecaster install, part 3