How to change language on an iMac

On the login screen you will see a field on top. If you click through it, you will eventually hit the language field. Select your language and away you go. It is under the Mac OS X logo, and the "networks available" field. You will see an American flag and that is where you change it. I assume this is what you mean.

System Preferences (it should be on the dock and look like a set of gears, or the fourth one down on the apple menu)>Language and Text (it will look like the blue flag).... english is at the very top.

Try to find in settings...it in the right corner...about Mac etc.