1. Download the App from App Store or Google Play
2. Press on the + icon and choose a Generic SIP account
3. Enter the details: Title, Username, Pass, Domain, and choose the Push Notifications. After that, press the Advanced settings
4. Choose TLS (SIP) in the Transport protocol. Press Done
If you want to change the Ring tone. Go to Accounts / Advanced settings / Ringtones
Record Voicemail