CE 6 is very old and is no longer officially supported [current stable version is 13.4.0]. That said, the Kaltura Server was always configured on top of Apache in it’s own VHost so the SSL configuration is the same as with any Apache VHost.
Find out which file contains the Kaltura Apache VHost config with:
# apachectl -t -DDUMP_VHOSTS
Then edit that file and add the needed SSL directives. You can look at https://github.com/kaltura/server/blob/Mercury-13.4.0/configurations/apache/kaltura.ssl.conf.template as reference.
Next, you’ll need to edit /opt/kaltura/app/configurations/local.ini and /opt/kaltura/app/configurations/admin.ini so that instead of http://$SERVICE_URL, https://$SERVICE_URL is used and reload your Apache.
I’m assuming here that you are running an all in one instances of Kaltura, as opposed to a clustered ENV. If running a cluster of CE nodes, you are better off using a load balancer and SSL offloading, i.e: LB is configured to accept HTTPs requests and then makes HTTP requests to the different nodes.
Any LB that’s capable of sticky sessions can be used for that, you can see some configuration templates for Apache mod proxy and HA Proxy here: