The following steps will guide you through assigning a fax number to a user account:
Login to your admin account
From the main view, click on the "numbers" option on the left panel
Click the settings icon to the right of the number you wish to assign
Click the "add" button under the number users section
Choose the user you want to associate to the number
Note: You can repeat this step and add as many users to the number as you want
You should now see the username in the number users section at the top.
You have now assigned a fax number to a user account.