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If you return no results after each one of these searches (i.e. the People card is as it appears in the screenshot, above), or the results returned do not match the Person in question, then you've confirmed the User does not currently exist in the system. If this is the case, follow the steps laid out in the "Creating a New User" section.Registering a New User" section below.
If you DID find a user via one of those searches that DOES match the user in question, then you'll want to follow the steps laid out in the "Linking a Registered User to an Existing User" section below.