Finally managed to figure out that I need to write .post in the jQuery Selector box to get it to work! This should be made more clear!
This however isn't my problem, now that I have got it to work it makes the YouTube video break the post container. See http://www.max-palmer.com/video/lynch-sisters-bts/ for example. The plugin I am using to embed the YT video is 'Enhanced YouTube Shortcode'. Any guidance to fix this problem will be greatly appreciated, as I don't really want to leave my website looking like that for very long!