This tutorial walks you through the process of creating an index.php file, being able to run the php file on a local server, and being able to dynamically update the page in a browser using Prepros.
Go to the folder where wamp is and search for the www directory.
Usually, if you have not changed the directory location upon install, it will be here... c:/wamp/www/
In this directory, create a folder, or add a folder of you choice
If you add a folder, make sure the file that you would like to launch is named index.php