Sorry I messed up on the steps putting step 3 twice, I'm new to this editing software so I don't really know how to use it. Make sure to subscribe and hit that bell to make sure you see all my future tutorials!
Steps in text:
Step 1: Go on YouTube.com
Step 2: Search "YOUTUBE_RED"
Step 3: Go to the video "RedTube"
Step 4: Watch the video for 1 minute or more
Step 5: Go to the YouTube home screen, and enjoy
If not working, try watching the video for more then 1 minute.
It took me 3 tries to get it to work.
If the video is not appearing, filter it by "4 - 20 minutes" and see if that works.
Hope this helped!