To download YouTube movies:
1) Launch the vid on the YouTube website (not in the window on this page)
2) Go to the address bar at the top of the page
3) Type the letters "ss" right before the word "youtube" but after the "www." For example, if the address bar says "www.youtube.com/watch/xyz123.....", you would put the letters "ss" in the address bar so that you end up with "www.
ssyoutube.com/watch/xyz123....."
4) Don't type anything else or change anything else and hit "enter"
5) It will then take you to a website called "savefrom.net". Once there, you'll have the option to download it
6) Under "download link" on the right, you'll see a couple of download options (resolution, format, etc..). Click the resolution you want (don't click anything else) and a pop of window will appear asking you where you want to download and save the file to. That's it.
Here's a screenshot. It's outlined what and where you need to click.