First, you have to download VNC client ( https://www.realvnc.com/fr/connect/download/viewer/ ) and install it (default options are good).
Next, the extenso and your computer must be connected on the same network (it won't work if your extenso is connected via 3G).
Go on the extenso and find the IP address :
* for ethernet, click on "ETHERNET" in connectivity
and note the ip address
* for wifi, click on "WIRELESS" and then on the network on which you're connected
and note of the IP address
Once you have an IP address, start VNC Viewer on your computer:
And enter the IP address in the bar at the top of the application:
And then press ENTER.
It can take some time to connect. If you have a warning message like that
just click on "Continue".