You have to go to youtube  pick your video and copy the http code and take it to this site

https://www.tools4noobs.com/online_tools/youtube_xhtml/

 put the http code in the box on top that says you tube embedded code or url

 Then add a size  example  400 wide    x 400 height

check autoplay if you want it to autoplay

 then click generate code

when the code shows  Copy and paste and put it in what section you choose, dont forget to save,,