Any LinkedIn connections can be imported as a contact record or imported as a candidate record in the ApplicantExtra. This can be done using the Browse LinkedIn option (Side Menu->Home).
This opens the LinkedIn website where you need to login to your LinkedIn account. You can then search the required connection and click Import as Candidate or Import as Contact to import this connection as a candidate or contact respectively.
If you import the connection as a candidate, you need to map the LinkedIn attributes to the ApplicantExtra attributes and save the changes to create a Candidate Record.
If you import the connection as a contact, you need to select a client or create a new client and save the contact for this client. This will then create a Contact Record.
You can see Browse LinkedIn for more information.