Find a spot near your main panel—ideally within arm’s reach. Screw the transfer switch box to the wall using heavy-duty screws. Make sure it’s level, unless you’re going for that “leaning tower of power” aesthetic (hint: don’t).
Now, run a conduit (that’s the metal or plastic pipe for wires) from the transfer switch to the main panel. This part is like plumbing, but for electrons. If you feel like a tiny electrician–plumber hybrid, you’re doing it right.