Create an extension

Go to the menu Applications and submenu Extensions. Click on Add New SIP [chan_pjsip] Extension.

Enter the User Extension, the Display Name and the Secret. You can either create a new Username or use an existing one for this line.

If you want to use voicemail, go to the Voicemail tab and provide a Voicemail Password and an Email Address (if you want to receive an email with the audio message).

If you are done, hit submit and apply config.