02-06-2013 04:27 AM
Welcome to BlackBerry Support Forums
If it is your Brother's phone then first do a backup using BlackBerry Desktop Software , once it is done perform a wipe on that device then create and use your own BlackBerry ID on that device .Check this KB for further help :
KB26694 : How to change the BlackBerry ID on a BlackBerry PlayBook tablet or BlackBerry smartphone.
To use BBM application we need BlackBerry Data Plan / BIS , if you don't have that then activate it on your account to use this Application.