Both websites work in exactly the same way. First, you need to find a YouTube video that you would like to download. Next, you need to copy the url of that YouTube video - e.g. https://www.youtube.com/watch?v=LlpY7cnL2QE
Now, simply open up either ‘YouTubeInMP4.com’ or ‘YouTubeInMP3.com’, paste in your YouTube link and then ‘Download’ or ‘Convert’. Your YouTube clip should now be downloading onto your computer!