Navigate to the Natterbox app using the Salesforce app launcher
Select the Natterbox Users tab
Select New Natterbox User (from Salesforce), this applies to regular Salesforce users as well as Chatter Free users
Filter by name or profile type and depending on your selection the results will appear at the bottom of the screen
Select the appropriate user by clicking on the tick box to the left of the name
Click Add Selected
Please note: the system will automatically assign the lowest available extension number within the Natterbox range (2000 - 7999) if none is defined while adding the user. This can be changed later.
For a video walkthrough please see below: