To import a single YouTube video and create a WordPress video post, go to plugin menu Videos, page Add New.
All you need to do is enter a valid YouTube video ID and hit Search video. If video is found, you will be taken to custom post edit page and, depending on your global settings for importing titles and descriptions, will have post title and post content already filled with the title and description retrieved from YouTube.
Categories, if option for importing categories from YouTube is checked, will also be assigned to the new post automatically.