How to set up your own nickname?

Hi, I recently turned on the “Friendly Names” option on my buddy list, and noticed that some of my friends’ screen names turned in to “friendly names” without me changing them to those names.

I was wondering how its possible to set your preffered “friendly name” that comes up when someone wishes to view their BL like that. My friends don’t know or refuse to tell me. :rolleyes:

Thanks.