Having the ISO file in a local folder, we need now to extract the file in order to execute the Office installer. For doing so, let's download the latest version of 7zip.
It is a very simple and light program. Once 7zip is downloaded and installed, right-click the ISO file, go to 7-zip > Extract Here.
Access the new folder created after the ISO extraction and double-click setup.exe to run the Office installer.
Let the program install, run and introduce the Product key when required.