Google made some changes on YouTube. Annotations were added several years ago. Add Titles, speech bubbles and other fun stuff. Now replaced with End Of Video Annotations.
Go to Videos. Click on one of your videos then Video manager.
Once on video manager click at top of page end screen & annotations, Then click on Add Elements.
The landing area within the video will highlight with a square. Above the video chose template and location.
Once you have the end screen annotations chosen. Make sure you Save,
These end of screen annotations will link to another video or the element you chose and will pop up inside video when 20 seconds is left on video.
Screen shot shows what the end screen annotations looks to the viewer.