You purchased and downloaded the 18in4 diet on your computer Where is your download?
In whatever folder you place your downloads into. Some people
use "my documents/downloads" on their machines. For instance, if
you are using Firefox as your browser, you would click on Tools,
Options, then look to see where your downloads are defaulted too.
You can modify that location at will ... jot it down so you might
know for future times.