how do i get my mac desktop from nj to az

Do you have all of the original packaging?

If you have the original box the iMac came in, use that and add bubble wrap that's available at most office supply stores.

If you have the original box and packing that wold be the best approach since Apple ships in those boxes.

If not, I would go to a box store, get a box larger than the overall height, width and depth dimensions of the iMac, and a roll of bubble wrap. Most shipping supply stores and Home Depot have rolls of bubble wrap. Make sure the iMac is well wrapped and if possible, get some styrofoam peanuts or the like to fill the extra space. And, of course, pay for shipping insurance so it is covered.

I agree with Ralph, because I had UPS ship my iMac across-country last year.

Make sure you don't slip the keyboard in the box up against the monitor; I taped a thick piece of cardboard over it. Make sure there's no movement of the computer or the power cord if you include that. Just imagine the box being dropped on its edge when you pack it.

Insure it & track it online. And if there's important data on it, back it up -- twice. I wouldn't ship the installation disks with it, in case you need them later.

And if there's personal data on it, I would erase the disk, too, in case it never arrives. I asked UPS to "require a signature" upon delivery; but after a week when UPS delivered my iMac, the driver saw my garage door open, dropped it off there and drove away. S/he never got my sig, nor rang my doorbell!

If someone had stolen it from my garage, they would have only found a blank HD, and not my Quicken files, photos, etc. I took the 2 external drives with the Time Machine backups on the airplane with me. (I showed the T S A folks what was in my carry-on bag, in case they thought its X-ray looked strange.)

Hope for the best, but plan for the worst.

Cheers!