Welcome to the Make community!
You can build the YouTube video URL simply by appending the Video ID after this:
https://www.youtube.com/watch?v=
e.g.:
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!