This changes does not effect your public name.This only changes your name that can be seen in the clan.
How to
Changing your name is an easy process. First, simply click the link below:
http://www.xfire.com/communities/1xg1/roster/
Then you will see this
(http://i1255.photobucket.com/albums/hh629/blazer981/xg2_zps74105432.jpg)
Enter the Nickname you want to use in the clan with your clan tag {XG}
(http://i1255.photobucket.com/albums/hh629/blazer981/xg_zps6b04ad1e.jpg)
Then Click on the button Set Nickname
(http://i1255.photobucket.com/albums/hh629/blazer981/xg3_zps4dabe03b.jpg)