In order to serve websites over HTTPS, you will need to generate an SSL certificate and optionally request an IP address from us.
Generate a Key and Certificate Signing Request, and then either generate a self-signed SSL certificate yourself, buy one from somewhere (search for "ssl certificate" using your search engine of choice for a list of popular vendors), or request a certificate from letsencrypt.
Add a stanza to your DomTool configuration file. Examples of this may be found at DomTool/Examples.
This relies on TLS SNI to work, which will work in almost all cases (the only notable software no longer supporting SNI is Java 6, which is deprecated). If for any reason you need a dedicated IP address, we are happy to provide you with one as long as our upstream providers will provide them.