How do you change an existing facebook friend to have a limited profile/ how do you change ur display name?

I was wondering how to change your display name so you can change your name to have one initial. I'm fairly new at it so I need some help. Thanks!How do you change an existing facebook friend to have a limited profile/ how do you change ur display name?
go to account settings, top right cornor of page



then you can choose privacy and other things to change that sort of stuff