Parm to post a YouTube video you click the YouTube icon and some text should show up like so...
[YT.][/YT.]
(Remove the . they are just to show the code.
Anyway!
Find the link to the video you wish to post...
https://youtu.be/FKXSh14svlQ
Now you remove the the text up to just the number and letter sequence after the last / which leaves you with this...
FKXSh14svlQ
Simply put that gibberish inside the first code like so...
[YT.]FKXSh14svlQ[/YT.]
Now once I remove the . The text will show your video like so...