Once you’ve purchased the Premium Key from the Google Play or Amazon app store, all you need to do is tap “Install”. It will “unlock” the premium features in Docs To Go Free edition. Once this is done, you can tap on Docs To Go Free edition or Docs To Go Premium Key to start up Docs To Go. If you’d rather not have 2 icons representing Docs To Go on your device, go to Docs To Go/Settings/Advanced and check Hide Premium Key.