You can search for a user by their name.
If you are an operator of a helpdesk, your helpdesk is not visible in the
    Collaboration window.
- 
                From the Collaboration window click the new conversation
                    icon  . .
- 
    Enter the user’s name or part of the user’s name in the Search Contact
     field and press enter.
    You must type at least 2 characters. This field is case insensitive. The list of
     helpdesks and users whose name or description matches with the search key appears when you
     press enter. 
- Click the contact’s name from the list to start the chat.
Tip: You can add this user to your address book so that you don’t have to search next
                        time.