Q: How to set up a Apple Cinema Display monitor to my iMac.

thunderbolt on the iMac? if so, you'll need an adapter i'd guess. if its the 30" cinema, probably a mini-display port to dual link dvi. course, you might not even be able to drive that size monitor off the iMac. I dunno. either way, you need a display adapter.

the monitor should already have a power cable, no?

yes, thats the correct adapter.

if there isn't a spot to plug in a power cable on the back then i'd assume it'd get power from either the firewire or USB.. more than likely the firewire. I dont have a apple display so i'm kinda running blind.

Katorama, How did you get on? I have just bought a 21.5" imac (non-thunderbolt) and hooked up to my 20" cinema display (A1081) and it is not detected. Light on the monitor is on but that's it. Would be interested to see if yours works.

Ahh, I have it working now. Make sure you plug the USB plug from the display into the imac (even if you don't intend to use the built in USB ports) it needs this to work! Best of luck.