Here you will learn how install Yandere Simulator.
To find out how to download the latest Yandere Simulator, see this article: How to download the latest version of the Yandere Simulator
So, you have the archive with the game, what to do about it?
First, you need a program called WinRar, you can download it here (it's free): http://www.rarlab.com/download.htm
Download WinRAR and install the usual way. Write a comment if this will be a problem.
Now open the downloaded version of the game, making double click on it.
You will see this:
Have a good time. And remember: This is a debug build.