The AV formats you can import into the FLV Editor are FLV, F4V and MP3. As for FLV, you could import from the media library or from the Internet Explorer cache.
Media Library is the area where FLV clips are stored in the YouTube FLV downloader program. If you choose this option, you’ll be taken to the free YouTube FLV Downloader, which you can download and install.
Files you download through the downloader could easily be imported into the FLV editor. For your information, the YouTube FLV downloader captures flash videos from MySpace, Dailymotion and other major video sharing sites.