Note: Upgrading will require the same language installer to be applied to the existing installation in order for the process to be silent.

You can download official installers from here:
https://www.seamonkey-project.org/releases/
Make sure to select the right architecture: Windows x64/Windows x86

Upload the installer and insert the following silent arguments: /VERYSILENT /NORESTART /S /quiet

After uploading the file, you need to select the groups or hosts to which you wish to deploy the package / updates.