Check out this website https://www.scirra.com/
As the tagline says : Construct 2 is a game maker for Windows that lets everyone create amazing games.
You'll have to download it (Click Download on the same page).
As you can see, all of this is very simple. Navigate through the website, read what it says, and you'll get it.
It does say "Create games. Effortlessly", but don't take that literally. You'll actually have to read the main page and download it. There,s only so much I can do for you.