I had to tighten the glove box latch/knob in my old 77 plow truck a while back and I took a pic that might be helpful. It's the non-locking type.
You have to flip the glovebox catch (labeled A) back into the closed position. Then stick a small screwdriver or similar tool into the access slot (labeled B) and depress the retainer tab on the knob/cylinder assembly (labeled C). That'll allow the knob/cylinder assembly to pull out without ripping off the chrome knob. If you don't flip the catch (A) back into the closed position, the retainer tab (C) won't be accessible through the slot (B).