[Koha] Need help in moving to HTTPS using Certbot on Ubuntu 18.04

[Tim Auld]

Hi Everyone,
I have had Koha up and running for several years at the Northern Philatelic Library. It has been running without the benefit of HTTPS certificate security because when I installed Koha I couldn't get SSL to work. Yesterday I tried again to get SSL to work. I used Webmin to setup Apache2 Virtual Hosts and used Certbot to create certificates for "library.norpslib.org" and "library-intra.norpslib.org". Unfortunately I still couldn't get it to work.

The first problem I had was 403 security errors. I got past that by telling it to Follow Symlinks, but then just received a list of the files in the Document Root.
Could someone please point me in the right direction for detailed instructions on how to move a Koha site from HTTP to HTTPS?
Thanks for any help you can give me.
Regards,
Tim Auld
Webmaster
Northern Philatelic Library.