In order to post this option to your Moodle course, you'll need to select the activity "Kaltura Media Assignment."
You can look at documentation for submitting videos into assignments.
You can also look at documentation for creating an Express video directly into the Media Assignment (not a Capture video)
In order to use Kaltura videos for a forum, use these instructions.
You can also create an Express video directly in a forum. (Not Capture)
Adding Kaltura Video to Discussion Forums
Click the name of the Discussion Forum
Start a new thread, or click reply (it will depend on the forum settings your teacher has used).
Click the Kaltura media icon
A pop up window will appear. If it doesn’t, check your browser's pop-up blocker settings.
The pop-up will connect to your Moodle My Media area.
Click “Embed” next to the video you want to add.
Or, click Add new to upload the file or record a video in Express Capture.
A weird looking link will appear in the discussion forum post. When you hit save, it will turn into an embedded video.