To update an Airgap installation, you will need to download a new package via a link that we provide you and upload it to the server location specified in the "Console Settings" in the management ui.
To download the package onto your computer, you can use something similar to
wget --trust-server-names -O your_update.airgap "link_we_provide"
Then to upload the package onto the host machine, you can use something similar to
scp -i ~/.ssh/your_key.pem /path/to/updated_package.airgap ubuntu@host_machine:/path/to/updates
On the dashboard in the management ui, you can now click "Check Now" and should see the new update to install.