For iOS and Android
Download and install either the Grandstream Wave or the Zoiper app from the iTunes App Store (also available in the Google Play Store). For the configuration steps below, refer to the Administrative Info article containing your server- and extension-specific information.
In the Grandstream Wave app (Zoiper setup is similar):
1. Select the SIP Account option
2. Enter an Account Name and Display Name
3. Enter your SIP Server address
4. For the SIP User ID and SIP Authentication ID, enter your extension
5. Enter your SIP Registration Password in the Password field
6. Optional: To use your softphone on a cellular network, go into Advanced Settings and disable "WiFi Only"
7. Optional: Many apps are configured to stop working when in the background or when the phone is in low power mode. On an iPhone, tap Settings / General / Background App Refresh and tap the button next to your softphone app.
For Microsoft Windows
Download and install the VitalPBX Communicator.