Point your BlackBerry browser to blackberry.com/messenger and see. If that doesn't work, use your BlackBerry browser and visit mobile.blackberry.com and look for a link to BlackBerry Messenger.
BBM was released back in the day when I had the 7100t and I had it then. Don't know if RIM is still supporting versions for devices of that vintage now or not. If so, you should get it through either of those blackberry.com pages. Posted via BlackBerryForums.com Mobile