Before installing the app — go and create the SIP account for your agent.
Once you install the application on your computer, configure your Zoiper software settings in a few steps.
When you start ZoiPer for iOS for the very first time, it should automatically take you to the "Account" screen. If this is your first SIP account, you should see a setup wizard that looks something like the first image below.
Click "Add Account +" (if necessary).
Answer to the question "Do you already have an account?" => "Yes".
Choose "Manual Configuration".
Then choose an account Type "SIP Account".
Get the user information you gained in the main SIP-accounts settings article and put it into the corresponding fields.
In the "Additional Settings" section, select "Audio Codecs" and choose GSM, a-law, and u-law.
The device should display "Registration Status: OK".
Your device is now registered.
Once you set the configurations — make a test outbound call to check the connection.