Replace hostname.scene7.com referred to below, with the applicable domain used on your website.
Replace [IP] with the IP address of the staging server, applicable to your region.
Testing for success:
Note: If you have trouble changing your hosts file, see here or contact your local IT helpdesk
Mac OS X 10.2 or later
Edit the /private/etc/hosts file. For more information on how to use the hosts file, open Terminal and type: man hosts
Note: Editing this file requires root privileges.
Mac OS X 10.0 through 10.1.5
Do a ping on the domain you use - you should see the IP address of the staging server, which you entered into your hosts file. http://www.wikihow.com/Ping-on-Mac-OS
Go to your website and test your images and viewers. Check that any commands are applied correctly. Note: you could encounter broken images while testing if the staging environment being out of sync with production.