It's as simple as copying the URL of the video that you want to download, pasting it's address into Vixy, picking what format you want to convert it to (AVI, MOV, MP4, 3GP, MP3) and hitting the start button. Once Vixy resolves the video address, it will convert the flash video from Youtube to the downloadable format that you picked. Then all you have to do is download it to your desktop.
Piece of proverbial pixel pie.