Plumbing it is pretty simple...run your supply down into the pan where you've located the valve, then back up to the WH inlet. It's your choice if you want to then use the internal switch to disable the burner if it trips. You're done. If it does get enough water in the pan, it trips (about 1/2" if I remember).
You could use that switch to trigger your alarm system as well, if you wanted.