If you're using either Standard Editor or Enhanced Interface, you'll find an icon of film on the reply/post box. When hovering your mouse cursor over it, it'll say "Insert Video". Click on that button and bring the exact YouTube URL you want to show.
I have an IPad Pro and not a computer anyway, so the way I do it is click share under the Youtube video in question, select all of the link there in the box, and then copy and paste it into TBT and add the video code to it. Just thought I would share that with you.