Installing Comsol from iso image

You've got the installation for Windows. You need to use the installation for Linux.

You can get the installer for Linux from the Comsol website: https://www.comsol.com/product-download

and select the appropriate options (version of Comsol and type of operation system Linux/Windows/MacOS) If you are performing the download on a windows computer then standard settings will make you automatically download the iso for windows)

Using this link you will go to the specific site to download the Linux version but you may still wish to change the Comsol version depending on your license: https://www.comsol.com/product-download/5.3/linux