Each Youtube video has a code - for example:
https://www.youtube.com/watch?v=7ssp7bRgZaM
You are interested in all the info AFTER the question mark:
https://www.youtube.com/watch?v=7ssp7bRgZaM
All you do is cut that out:
v=7ssp7bRgZaM
Then highlight it by holding the mouse button down as you drag it across all the characters - it will turn blue - then just click on the YouTube app: