How do you replace the casings around the spark plugs and wire boots on a 2000 pontiac grand prix gt?

The metal casing that goes around both the plug itself and the boot that connects the wire to the plug came disconnected while i was trying to replace spark plug wires and I can't seem to figure out how to put it back on, no matter how much force, pressure, angle, etc. I put on it. It's basically like it refuses to go back where it belongsHow do you replace the casings around the spark plugs and wire boots on a 2000 pontiac grand prix gt?Go to an auto parts store and get new ones. Also, get spark plug silicone and put on tops of spark plugs.