Enter the sign-in address of the Skype for Business user you wish to add (usually their U of I email address). For example, email@example.com.
When Skype finds the match in the search results, look for the word "Skype" below the Lync user’s name. If "Skype" is present, this indicates that Skype has located the Skype for Business user's address. Click their name.
In the top right corner of the window, click Add to Contacts.
The new contact is now added to your contact list; however, you
will see a question mark instead of their status icon until they accept
your request. When your new contact accepts your request, you will be
able to see when they are online, when they initiate IM conversations,
and when they make audio calls.