1. In the search box type a name or desk phone number (if they are in your organization). As you type, search results will start appearing below the search box and the tabs will change from "Groups, Status, Relationships, and New"
to "My Contacts and Skype Directory"
2. If the person you are searching for is in your organization, keep the My Contacts tab selected (that's the default). When My Contacts is selected, Skype for Business searches in your organization's address book.
3. When you see the person you want to add, select their name. Right-click and select Add to Contact List.