Ive never installed one without a cage. Im sure the cages are quite universal might want to stop at your stereo place and ask for one.
edit: might have read your post wrong, do you have that cage or not.. lol
If you have the cage, slide that over the deck, then slide the deck into the install/dash kit. There are usually fins that you can pop out on the cage to hold it onto the dash kit.
Youre dash kit should have some way of mounting to the dash or some even just fit in there without screwing them in, depends on the dash kit.