The above are the basics that you should know. For an expanded dive into the content tool, there is a content playlist from the vendor at: https://bit.ly/2P9Tu8C
If you are thinking about adding a video to your course, you can use https://www.macvideo.ca, or Stream within the Microsoft Office 365 suite of tools. Alternately, use Vimeo, or YouTube to host your content externally and embed the video on a page in Content. Remember to respect copyright and accessiblity laws when you are using other’s work as a part of your course. For more information about copyright at McMaster, please go to http://www.copyright.mcmaster.ca/ . For more information about accessibility please go to http://accessibility.mcmaster.ca/teaching-accessibly . Below is a video demonstrating how to embed a video or create content from scratch in D2L which we call Avenue to Learn. The process for embedding a video from YouTube and almost any other video streaming site is the same.
Adding Release Conditions to Content Items
You may want to restrict access to Content items based on other activity in the system (eg. discussion posts, enrollment in a group or completing a quiz). This video demonstrates this ability.