Hi JeanWilson.
To configure to the agents comunicate through HTTPS protocol you have to switch the configuration in the target agent settings.
In your Altiris console, click on Settings > Agents/Plug-ins > Targeted Agent Settings. Choose the policy name, probably is going to be the first one (All Desktop computers (excluding Site Servers)), go to the Advanced Tab e check the option to "Specify an alternate URL...". Click on the "Pencil" icon and choose the HTTPS URL.
In the next update that all of your agents in this policy name will switch the communication to HTTPS.
Regards,