click here http://edit.xanga.com/editaccountprivacy.aspx and look at the 2nd box

also Xanga offers three specific privacy settings:

"Signin Lock" - only users on the Xanga network will be able to view your site
Footprints Lock - only users on the Xanga network displaying footprints will be able to view your site
"Friends Lock" - only users on the Xanga network you have designated as friends will be able to view your site
Please note that if you choose to put Friends Lock or Footprints Lock on your site, Signin Lock will also automatically be added.

in this case you want to click "friends Lock"