I think you're talking about that little button near the Shifter, on the Shift column...

Watch this video YouTube - Pontiac Key Release Ignition Problem

At 50seconds in, it will show the little round cover on the underside of the steering column that you need to pop off, and how to depress the tumbler release. It's really damn simple, and if you need any more direction at all, i'll go out a take a few pics.

Hope that helps