Click the Contacts tab, and then click in the Search for Contacts text box. Type the Microsoft account of the Skype user that you wish to add, control-click on their contact card, and choose Add Contact.

1) Click Contacts, then click Search for Contacts and type in the Microsoft account name of the Skype user you wish to add.

2) Control-click on the user's contact card, and click Add Contact.

OUTCOME

The Skype contact will now be added to your Skype for Business contacts.