You tube video link.

If you're using the desktop/ mobile version then simply copy the url (link on the top) and paste here. It will automatically hyperlink.
If you're using the app then there's an option of "share" below the video. Simply copy the video link and paste here :)

It should show where you write it (if you're mentioning it in a question)

Thank you so much.
I am using the app. And I followed what you said. And I got it.

Glad to help :)