If you had a white retainer, then the transponder will just slide out. If you did not have a retainer, then your transponder is glued into place, and you must extract it.

Slide a thin blade under the transponder and GENTLY pry it up. I say gently not becasue the transponder is fragile - it is not fragile - I say it because the transponder is SOOO important. Without it, your car won't start!! So be careful not to damage it or lose it.

Note that the transponder is pushed a little bit forward into a small recess in the front of the case. So it will not pry all the way out. Just pry it enough to get a grip on it and pull it out the rest of the way.