Unable to Start

ggmagic1​  This error is typically antivirus-related.  So please set exceptions in your antivirus for TS4_x64, TS4_DX9_x64, and TS4_Launcher_x64, or the Bin folder they're in.  Set an exception for EADesktop.exe as well while you're there.

You may need to repair the game again afterwards.

Follow up question: How do I do that? How do I access my antivirus? I have no knowledge whatsoever when it comes to technology.

ggmagic1​  Open Windows Settings > Privacy & Security > Windows Security > Virus & threat protection.  This will list the antivirus you're running.  Google "[antivirus name] add exception" and look for an article from the publisher itself that covers adding exceptions or exclusions.  Most publishers have reasonably-good documentation on their websites.

I followed your instructions and it led me to this. Not sure what anti-virus program I am running or even if I do have one running.

ggmagic1​  That looks like Windows Defender, but you should definitely restart the service, and then restart your computer, and double-check this page again to make sure it's Defender and not some other antivirus running.  Here's a guide for managing Defender:

https://crinrict.com/blog/2019/03/windows-10-defender-controlled-folder-access.html