Enter your AWS + Cloudfront settings in Admin -> Settings -> General Site -> File System Tab
After change your settings, go to media section to clear cache and fetch files from the new media server.
To Use the image editor, you need to configure the cors for AWS and Cloudfront, this link contains the steps to configure it:
Also, review this to ensure the cloudfront configuration:
If you configured well both, you will see like this:
Enjoy Camaleon CMS the best CMS for Rails.