New Installation – Server Doesn’t Process Index.php

I recently installed the newest version of WP. The 5 minute install creates my database structure along with a username. However, I get the site’s directory tree instead of going to the index.php page. I can type it in manually and it works, however. My WP files reside in a folder called wp off of the root directory. If I type https://www.mysite.com/wp I get the directory tree. If I type https://www.mysite.com/wp/Index.php I go to my WP home page. Does anyone know how to fix this?