This is a picture of what you will see when you get the trunk latch out of the way. Remove that nut with a socket wrench and pull the washer off with the nut. That will leave a split, funny looking tube thingy that is pinched onto the back side of the lock cylinder bezel. The split tube thingy will pull off of there.
The next two pictures are the entire assembly. The first is full assembled, minus that pesky trunk lid, and the second is everything disassembled.
This last picture shows the release button for the lock cylinder. You just depress that button with the key in the lock, turn the key a little bit so that the key won't come out of the cylinder when you pull on it, and pull the cylinder out. If the reason that you are replacing the cylinder is that you have no key for it, you can also take a very small flat-bladed screwdriver and get behind the cylinder with it and, with the button depressed, pop the cylinder out like that. The rod sticking out of the back of the bezel is a seperate piece that you will need to put back in before you install the new cylinder, or put your old cylinder back into your new bezel. Whatever it is that you are trying to accomplish here, drop the rod into the bezel, put the lock cylinder into the bezel, making sure that the tab on the end of the lock cylinder is lined up with the slot in the end of the rod, put the trunk lid gasket onto the bezel, put the bezel into hole in the trunk lid, put the split tube thingy onto the bezel from inside the trunk, put the washer and the nut on the bezel and snug up the nut. It doesn't need to be tight enough to have the bezel squash the gasket and crack the paint.
As a side note, if you have accidentally locked your keys in the trunk of the car, ( hey, it happens ) what you do is, on a coupe or a convertible remove the upper part of the back seat and take a half inch socket wrench with about 3 miles of extensions on it, and remove either the two bolts holding the trunk latch to the trunk lid or the two holding the the other part of the trunk latch to the taillight panel area, whichever you can get to the easiest. If you have a fastback, crawl through the trap door and do the same thing. You might have to remove that rear carpeted piece to get the trap door open, depending on how well the trap door is adjusted, which is usually not very well.