What version of cpanel has your host provided you? There is an "ssl manager" icon on both my cPanel X equipped servers.
I think MrBenn is right when he said "By the way, if your site is using cookies for authentication and you're using SSL to protect these, then having non-SSL and SSL available on the same subdomain (ie
www.) pretty much makes SSL pointless for that purpose."
http://www.cpanel.net/docs/cpanel/
A Google search turned up any number of SSL resources as well.