Do you have BB Desktop Manager? If so, it's fairly easy.
Go to Synchronise from Main Menu and click on . . .
Synchronisation : Configure for desktop .... then click on . . .
Reconciliation - Select what you want to do and how . . . then click on . . .
Synchronise (at the top): Tick what you want it to do (I just use it for contacts so I tick 'synchronise organiser data' and 'update device date and time').
. . . . and then synchronise, and follow the prompts.