You do not need to remove the account. Open Contacts hit the menu button and click "Get Friends"
From there you will be able to select friends from your Facebook or Twitter account. Select the friends you want to add. the names do not have to actually match, although it works better if they are the same name.
If they are not the same name simply select a contact int "Contacts" from your phone/gmail/corporate and scroll down to Linked Contacts, tap it and it will give you an option to select a contact to link. Tap that person FB account, then those two will be tied together.