Watch your video and grab the link in the URL Bar. Basically, this is the link to the page with your selected video on. For example, http://www.youtube.com/watch?v=QSuzIaOfgAU
Copy and Paste the URL into the white space above. Press the arrow to begin the download! Make sure that the .FLV extension is included when you are asked to Save As.
Also, if you haven't got one already, you need a .FLV player to play the video files. Don't have one? Click the speech bubble on the right to download it.