What distro of Linux are you running. Some such as Mandrake come with SSL pre installed.
Standard web traffic communicates on port 80, but SSL (Secure Socet Layer) uses port 443. The easiest way (if you can) is to install a distro that comes with SSL installed.
HTTPS = SSL... The prefix of https tells the web server that you are going to communicate over a secure connection, SSL.
If you can not reinstall the entire OS, then you are going to have to recompile apache with mod_SSL installed. Unfortunatly I do not know of an easy way to tell you to do this. However for configureation you can look at webadmin.
Sorry dont have more information...
PHPdev