You will need to visit the following page on a computer that is connected to the internet in order to download the installer
https://www.arturia.com/products/audio/minifuse/start
Alternatively, you can locate the installer in the Arturia Resource pages.
https://www.arturia.com/support/downloads&manuals
Once you have downloaded the installer, you can transfer it to a USB drive and connect it to the computer where you wish to install.
Firmware updates are handled through the MiniFuse Control Center application.
The application will automatically check for firmware updates on launch and alert you whenever an update is available.
To check manually, click the Gear buton in the upper right corner and it will bring up the firmware update window.
If a firmware update is available, the Upgrade to Latest button will be active.
Click it to download and install the latest upgrade.
If you computer is not connected to the internet, you will need to download the firmware update file on a different computer that is, and transfer it onto your computer on an external drive.
You can then use the Upgrade from File option to select the firmware file.