The hard way to do this is to enable SSL for the site (as a host), and then changing every single page on the site to be a "secure" page.  To make that easier, you could run an SQL query to change all of the pages in one fail swoop like this:

UPDATE [dbo].[tabs] SET [IsSecure] = 1

Or using the SQL page in the Host menu:

UPDATE {DatabaseOwner}{ObjectQualifier}Tabs SET [IsSecure] = 1

In order for that to take effect, you will need to clear the DNN cache.