Currently upgrade is only supported from Linux/Unix platforms.
Download WISP-Dist package distribution (.zip) and uncompress it in a separate directory on your workstation.
If you do not have upload-wdist script on your workstation, download it. This script requires scp & ssh.
Login to the target router as root and select "Start upgrade procedure" option from the main menu.
Run upload upload-wdist on your PC. Specify the remote host IP and directory with packages as the parameters.
Switch back to the screen with the remote router running "upgrade-wdist". Follow the instructions.
The system tries its best not to upgrade configuration files which were edited. In order to do this, md5 fingerprints of all read-write files are kept and are compared during the upgrade process. If file's MD5 fingerprint is different, it will not be upgraded.