To upgrade a Protel v3 PBX to version 4, the disc drive must be wiped clean and a new server operating system installed on it.
Follow the preparatory instructions here
After the new Ubuntu 16.04 system has been installed, nexMatrix will help you with the required network settings. The installation of Protel v4 is done via a remote SSH connection. You will need to have the ability to forward port 22 TCP to the LAN address of the PBX.
The final step after the updated software is installed will be to apply your PBX backup file. This will restore complete functionality to the PBX if it was deployed in a production environment.
The entire process takes about 2 hours. Please schedule this with your account representative, or directly with nexMatrix support.