HTTPS is an easy process, but steps must be followed in order with sufficient time between some of the steps for the web addresses to take effect in the dream host servers.
Setup a direct pointer to the subdomain to the appropriate WordPress Network. Note that this overrides the *wildcard address that has been in use.
Wait at least 10 minutes for the Dreamhost routers to put the subdomain address into effect.[UNKNOWN] How long before the subdomain is recognized by name servers throughout the internet?
Get a SSL certificate for the subdomain.
Wait at least XXX minutes/hours for the certificate to take effect
Change the internal address for the subdomain within the WordPress network to the HTTPS address.
Voila! There may still be an issue of HTTP links on the page (most commonly to images or internal pages) that were setup as http://subdomain.usnaxxx.net that will need to be set to HTTPS, or else browsers will continue to give security warnings.