To upgrade the SSL Visibility software you'll first need to download the software image from the Symantec Network Protection Downloads section.
NOTE: The SSL Visibility appliance supports only one upgrade method in the 4.x version vs the three that are available in the 3.x versions.
To upgrade via WebUI, login, then go to the Top Right Hostname > System Images
Please see the attached image for more detail
Choose your file and the process will start, when finished the device will prompt for a reboot.
NOTE: You can also download the image directly from our support page here if you have the full URI. However, it is recommended that you download the image and use the upload function.