Well, try with some more information for a start. What steps have you undertaken, what happened at each step, any error messages, which version of Windows, what spec iMac...
I am using a superdrive and the new 27 inch iMac, 1TB Fusion drive. I'm trying to install windows 7 ultimate via bootcamp, but once bootcamp restarts the computer for windows to install, I see the dos interface with only a blinking line - the line you see to mark where you are on a document.
Make sure your copy of windows is the retail version. The Oem, student, etc versions typically will display this blinking cursor forever and a day, there are work arounds, but you'll have to google the solutions...
The new iMac doesn't come with an optical drive, right? And, from what I've read, the Windows installer doesn't play well with external disc drives. Best course of action may be to have Boot Camp Assistant create a bootable Windows thumb drive.
Insert your Windows disc and open Disk Utility. Click New Image. On the window that pops up, choose DVD/CD master as the file format and click ok. (This will create a .cdr file.)
Then open Boot Camp Assistant and check the box beside Create a Windows 7 install disk.
You may need to change the .cdr extension to .iso, but I think BCA will recognize the file as is.