Hi jab8888 - I'm sorry you're struggling with this. I'm a bit unsure what I was thinking 9 months ago, but I expect some sort of video <div> container and other HTML that needs to be added to the appropriate templates. Figuring out which template to actually place this HTML on is the challenge. Sometimes it's easy, other times not.
I believe there's a plugin that aids you in doing this. I usually just add a HTML comment with the file name at the top of all likely candidates, then load the target page and examine the page source code. The comments show up nicely in the syntax highlighting of most browsers,telling you what templates are used where in any particular page.
I would expect you would use both CSS files if the author took the trouble to make them available. Put these in a subfolder of your child theme because your theme already has a style.css file. Don't confuse the two!
The usual problem people run into when adapting generic tutorials to WP is instructions to place meta links, style, and script in a page's <head> section cannot be followed exactly. WP inserts these sort of things for you once you've enqueued the files using
wp_enqueue_style(). These functions are called from within an action callback function you create that is hooked to 'wp_enqueue_scripts' with
add_action(). This hook works for enqueuing styles as well. All of this code goes on your theme's functions.php file.
The trouble I usually have when setting this stuff up is getting the paths all correct. Checking the page source, access log, and Apache error log are useful in checking that all paths are correct.