This plugin is designed to access a facebook feed and display it in a WordPress Widget.
Look for "Facebook" under Appearance -> Widgets. Drag it into a sidebar, type your Youtube name ex:109122432465903 into "Facebook Account ID" then choose the number of posts you wan't to display. Click Save.
There are many methods to find your Facebook ID. You can either Google the methods or use this easy method at http://findmyfacebookid.com/ to find your Facebook ID.
Caching keeps a local copy of your posts at the interval specified so you don't have to constantly contact Facebook. This saves on site load speed because you don't have to make an external connection.
Try disabling the cache, saving, refreshing the page where you widget displays, then turning cache back on. Cache saves data into wordpress, so updating settings won't reflect until the next cache update.