I am trying to install a MacOS 10.10 virtual machine on my Mac 10.13.6 MacBook Pro using VMWare Fusion 10.1.5. I have a 10.10 installer with the .app extension. When I try to use the .app extension file as the ISO, it appears that things are installing up properly and then I get a notification that "This copy of the Install OS X Yosemite application can't be verified. It may have been corrupted or tampered with during downloading." I found a YouTube video with the 10.10 ISO file download link in the notes (ISO Image of MAC OS Yosemite 10.10 How to install on PC or virtual machine - YouTube ), but I was hoping someone could point me to an apple.com site to download it from as I don't like downloading files from unknown sites/persons.
Thank you in advance for your help!