Clear Youtube

I have a YouTube account and I made a playlist and ad to it.
Everything works good but I meet help understanding one thing?

If I go to the left hand side bar I see MPlaylist. History. Watch Latter.

If I go into Watch Later how do I Empty it out you know Clear it?

And how does anything get put into Watch Later?

 

Videos that get put into watch later tend to happen when you click add to and then click watch later, it can happen by accident on mobile or on the website from your computer, I have done that on occasion on my account as well. To remove them from the watch later page, from your computer, click watch later on the left side and as you hover over each video, there should be an X in the upper right corner of each box next to more. Just click that and each video will be removed from the watch later playlist. The other option is, if the videos have been watched already, you can click the remove watched button and that will remove the videos as well.