1. Log out of Second Life Viewer 2 (if logged on).
2. Go to the \skins directory of the directory you use for Viewer 2.
3. Rename sub-directory 'default' to 'default_backup'.
4. Add the 'starlight' folder to the \skins directory and rename 'starlight' to 'default'.
5. To uninstall simply delete the 'default' sub-directory and rename 'default_backup' back to 'default' again.