It's either in one of three places (that I've seen and worked on).
A) about a foot below the battery box/holder on the wheel well
B) on the firewall (same side as battery)
C) on the wheelwell/fender
Having said that, I've seen them all over the engine compartment, but the above are the most common places.
To locate it, trace the battery cable from the battery if you can't see or locate it.