In addition to adding contacts from your own workgroup, Lync 2013 makes it easy to add contacts that are external to your company, if the right permissions are in place.
In the Lync window, click the Add Contact icon.
Click Add A Contact That’s Not In My Organization.
Click the service the contact uses, such as Lync.
The Add Lync Contact dialog box opens
Type the contact’s messaging ID in the IM Address text box.
Select a group.
Select a privacy relationship.
Lync suggests External Contacts by default when you add a contact via this method.
When you instruct Lync to add ...