As Firepower said....flip that pivot plate to expose the key lock. Hopefully you will have a key that fits that lock. The original key was shaped like a football on the end just like the keys shown in two of the pictures in my post "Need a little help from my Fordbarn friends". If you don't have a key that fits that lock I can tell you a few ways to get the locking cover off so you can get to the lug nuts that hold the wheel and tire in place on its mounting bracket.
DO NOT PRY, DRILL OR CUT ANYTHING!! It can be removed w/o destroying any of those original parts.
Ask me how I know this 