i dont think you can, sorry.
It's permanent unless you get a new account!
You change your name on facebook by going to the upper right corner, selecting account, account settings, then theres and option to change your name and bingo.
yu go 2 settings (account settings ) then yu see your name and yu go 2 change and yu change your name! H O P E T H I S H E L P E D !
Edit one or two letter at a time over multiple edits. Sometimes Facebook will reject a name if you start adding all of them at the same time.