Many thanks, Mark!
I made the change you suggested and adding this one 's' to the wwwroot did the trick.
Just in case anyone else is having a similiar question, I had to spend some more time locating the right config.php file. In my case it was located in: httpdocs / config.php.
Also, there is some useful documentation on transitioning to HTTPS behind this link, which I wish I would've read before starting off