Any contact that is already linked will appear under Linked profiles. If you see the contact you want to link under Suggested links, tap it. If you don't see the contact you want to link, tap Choose a contact to find the right one.
To unlink a contact, tap that contact under Linked profiles, and then tap Unlink.
Note
Linking contacts doesn't copy or delete any contact information
from its source. For example, your Facebook information won't be copied to your
Exchange account, or vice versa.