Hi @kdobbin1,
While Kaltura is a 3rd party product not affiliated with Instructure at all, there are many schools that use Kaltura and Canvas together, my institution being one of them. I can try to offer a bit of guidance here... I will give a caveat that Kaltura is a highly customizable platform, so your school/institution may have things configured completely differently, but I'll try to hit on the most common config.
You are correct in general, that the Kaltura integration with Canvas will generally be done through embedding content in the rich content editor (textbox). There is another course level menu called Media Gallery where you can add videos for an entire class to see. Neither of these options is going to be great for messaging a single student though.
What you likely need to find access to is what Kaltura calls a Mediaspace or Video Portal. This is a website usually outside of Canvas where you'll be able to login, see the same media as you do in Canvas, but you'll have the option to change the video from private (only you can access) or unlisted (anyone with a link can access), then share the link with that single student via email. Unfortunately, we won't be able to help much in locating this site, since it could really be called anything. If you ask your school/institution Canvas team, they may know the web address or be able to forward the question to the appropriate people there if it's a different department.
I hope this helps!
-Chris
