/T switch makes it run recursively.
/reset, as the KB article explains, replaces the ACL on each file and folder with the default inherited ACL that just uses the ACL on the parent folder.
The last thing that was required was to run this command inside a cmd.exe shell with elevated privileges. You can do that by finding the Command Prompt icon in your start menu and right-clicking “Run as administrator”.
Be aware that mucking around with ACLs, if you don’t know what you’re doing, can seriously break your system in more ways than you can think of. It can also open you up to various attacks because of more relaxed permissions.