This can be found in the Client Portal.
You should see the word (admin) in the upper right of your screen. If you do not, you are not logged into the Admin portion and cannot edit as needed.
Click Line on the lefthand side
Click the Check box next to Activate to enable registration
Username: ********* (TelTel Account Number)
Display Name: eg: Bob’s phone (name displayed on phone)
Authentication Name: 09********* (TelTel Account Number)
Authentication Password: ************* (Matching password)
Register Address: voice.teltel.com.au
Register Port: 5060
Proxy Server Port: 5060
Then Click “Apply”