If you have opened a BlackBerry backup file with MyBB and only see a list of data types with no option to view or import it may be because your backup is a partial backup.
You do not need a full backup for the app to work but you do need a backup that contains at least one of the following databases:
Address Book - All
Calendar - All
Phone Call Logs
Without any of these MyBB will simply scan the backup and show you the size of the data that it found.
When you do load your backup MyBB will allow you to browse your data and choose what to import - the initial scan doesn't import automatically into the iPhone - that is a second step so that you can choose not to import things that have already been brought across.