Hello,
Your request is too ambiguous, so it's hard to help you. Nevertheless, I can answer partly. You can re-create private_html in any suitable way with FTP/SSH/Directadmin. If you need different content for sites on http and https, you really need to re-create directory. Otherwise you need a symlink, which can be created via directadmin web interface, to do that you need to visit «Domain Administration» page -> Select Domain -> Enable «Secure SSL» -> Click «Save» -> Check «Use a directory named private_html» -> Click «Save».
Of course you need a dedicated IP for the account and a valid SSL cert.