To add a contact to a certain address book on the blackberry you first have to be running OS version 4.1 and above and NotifyLink client 4.0.3.00 and above.
1) To do this you will go to the Address Book on the main screen, bring up the menu and select New Address
2) Bring up the menu and select Categories
3) Highlight the category you want and bring up the menu and select change option to select it
4) Bring up the menu and select save, add the contact and select save from the menu again.
5) After that you will see the contact in there.
6) The next PIM cycle you will then see the contact in that address book on the server.
7) To see if that contact was put in that category on the device, you can select filter from the menu, then highlight that category, select change option from the menu ,and then you will see all the contacts including the new one in that category.
8) To see all contacts in all categories, deselect it from the filter menu.