Look in the passenger footwell. I have an American Focus and if you're
sitting in the passenger side of the vehicle, the switch is to your right in
the passenger footwell. There's a sign with a gas pump and an arrow pointing
towards it. You just pop off the little piece of plastic and press the
button. Hopefully it's the same for your vehicle, if not, read the manual if
you have it.

Mojo

On my TDCi it is sitting in the passenger footwell, and it is not even
behind a cover. Just a simple sliding lever (down is normal, I think).