Tried to make site “secure” now i’m locked out

I tried to get rid of the “not secure” notification in the domain on my site. I read that you can add an “S” after the “HTTP” by going into the General Settings on your WP Dashboard.

After I did that my site is now down (error 404) and I can no longer log into my admin account found at mydomain.com/wp-login

Help!!

The page I need help with: [log in to see the link]