Location: rich text editor

Your ProcessWire site supports videos in a variety of formats, but for everyday use in any page, you can copy the URL and paste it in with no other formatting on the line - so it's on a line by itself.

YouTube:

https://www.youtube.com/watch?v=CxwJrzEdw1U&rel=0

To remove recommended videos at the end of a YouTube video, add (shown above): &rel=0

Vimeo:

https://vimeo.com/351995036

If you just see the URL, and don't see the video, make sure the paragraph tag surrounding the URL has no formatting applied (bold, italic, links, styles)...

It should look, in the source code like this:

<p>https://vimeo.com/351995036</p>