Open this url in your browser replacing YOURAPPID and YOURDOMAIN with your values respectively. I put it here as a reminder for myself. From time to time need this url template
http://www.facebook.com/dialog/pagetab?app_id=YOURAPPID&next=YOURDOMAIN

Also the facebook documentation about the subject can be found here:http://developers.facebook.com/docs/appsonfacebook/pagetabs/