Users in your PBX are found under the Company tab in the menu Users.
For each user, you need to consider several settings and parameters, such as:
Add user with:
Name, email
Add number (only those set up for billing can be selected)
StandardCallerID (can only be used by 1 user or queue)
Set additional services such as Call Waiting and Voicemail
Add Devices to the user
Set the profiles for the user
Set access groups