Changing the home directory for a WP install?

I am having trouble setting the home directory of my WP install.

Let me explain.

Ok right now I have my WP installed into https://www.mydomain.com/folder. In my hosting control panel I can point my https://www.mydomain.com to use the /folder as the home directory. Meaning a person does not have to type https://www.mydomain.com/folder to get my intended destination. But when I do that my WP install stops working. Any ideas how I can get this to work or why it does not work?