Here is the instruction on how to install the softphone application in order to make and receive phone calls from/ with your mobile phone:
You will find the icon for the instruction at the bottom right of the screen. Please select the "For Mobile" option.
Download the Zoiper application from the App Store and install it on your mobile phone.
Start the app and click on the icon at the upper left corner in order to scan the QR code.
Scan the QR code in the popup window on your computer.
Start using your extension to make and receive calls with Wifi network or LTE/ 3G data.