You an easily enable CDN in Magento by following these instructions:
1. In Magento control panel, go to Admin > Configuration > Web > Unsecure.
2. Update the following with CDN addresses:
CDN URL(eg, cdn.magento.com):
Base Media URL: cdn.yourmagento.com/media/
3. Save changes
4. Go to Magento Admin > Configuration > Current Configuration Scope: Main Website > Web > Unsecure > Base Skin URL.
5. Deselect Use Default for the Base Skin URL
6. Update Base Skin URL:
Base Skin URL: cdn.yourmagento.com/skin/
7. Save changes
Check your sites source code that is uses CDN. Picture links should be replaced with CDN URL addresses.