Here you go...from the BTSC:
To copy a contact from the Address Book on your BlackBerry smartphone to your Subscriber Identity Module (SIM) phone book, complete the following steps:
Note: Only the contact's name and phone number will be copied to the SIM phone book.
- On the Home screen, click Address Book.
- Click on the contact you wish to copy to view the details of the contact.
- Scroll to a phone number field that contains a valid phone number from the listing.
- Open the menu and select Copy to SIM Phone Book.
- Open the menu and select Save.
- Press the Back button to return to the Address Book.
- To view your SIM phone book, open the menu and select SIM Phone Book.