Please see: http://na.blackberry.com/eng/services/devices/#tab_tab_compatibility
Your Blackberry smart phone must be running Blackberry OS version 5 or higher to use this software. If you have an earlier version of the OS, you will need to wirelessly upgrade your device. If your phone is in the list of compatible phones displayed on the page we posted above, your phone can be upgraded to version 5.
To upgrade your device, go to Settings > Advanced Settings > Wireless Upgrade (your menu selections may differ based on the type of Blackberry you are using).