If you cannot get the key to turn in the ignition, then you might have a bad ignition switch and or lock cylinder. Try another key and see if you can get the ignition to come on. If not, the lock cylinder is bad and needs to be replaced.
I hear ha! I which there was a quick fix for this. But there should be nothing else that is preventing the key from turning besides a bad lock cylinder. SOmetimes something in the steering column can cause this.. but that requires disassembly of the steering column and is not an easy fix. Try a different key and see if that helps!