change keyboard for french-swiss version

bought a macbook in chicago 1 week ago. I select the french language when I started with the computer. I didn't have the right swiss-french keyboard. How could I change the locations of the letters of the keyboard?

Do you mean that your physical keyboard does not match the software keyboard you want to use, so you want to change the physical keyboard so the printed letters are in different places? If so, here is one place that sells different ones:

http://www.welovemacs.com/apinke.html

To change your operating system to French, just go to system prefs/international/languages and move French to the top of the list, and logout/login.