To get and upload the latest firmware
Navigate to Device | Settings | Firmware and Settings > Firmware & Local Backups.
Select the Import/Export Configuration option and save the .EXP file to a safe location by clicking on the export configuration option.
Click Create Backup > Retain Local Backup > OK.
This will save a copy of the existing Settings to the SonicWall non-volatile memory.
Click Products and locate the device you want to update. Click on the device serial number and select the Firmware icon to access the firmware version available.
Go to Firmware tab and click on the download button and save the file to a location on your computer.

Message appears to remind you to take backup of your current settings, click OK if you have taken the backup already.
It takes a few minutes to upload the firmware to the firewall, do not navigate away from the screen during this time.
Select the Boot Power Icon on the far-right. Once you click on the boot icon, the image will be first saved to the flash memory and then the firewall will reboot automatically.
The restart procedure takes place and the following screen would appear.