@Visionman,
Underneath the video display there is a row of buttons labeled with thumbs up, thumbs down, save to, share, embed.
When you choose the save to button, you're given the choice of saving to your favorites or your playlist.
I'd post a screen shot of it but I don't think I can get it done before this site goes down for maintenance this evening. If you still have trouble, post again and I'll get a screen shot for you next time I'm online and the site is up.