Whatever company offering you FTP access and hosting those files for you over HTTP should be setting up HTTPS for you automatically without any extra input from you. That’s why all the instructions assume command-line competence: designers are not the target audience; sys-admins are.

If your host hasn’t caught up with the times yet it’s very straight-forward to get this for free (along with other benefits) from cloudflare with a few clicks.

This is misinformed FUD.