Connecting a MacBook Air M1 2020 to MacBook Pro Early 2015 - for multiple displays in Logic Pro X

How do I connect my 2nd Mac (Catalina 10.15.7 MacBook Pro, Retina, 13inch, Early 2015) to my new MacBook Air M1 2020 (the host) so that I can use the 2nd Mac as a monitor for a movie that I am creating a soundtrack to in Logic Pro X?

I have an adapter that I can use to connect via HDMI and USB - but my problem is that I want to have one screen with the editing screenset for Logic Pro X and the older model to host the movie.

So I am not sure what I should be doing? Screen Sharing? Setting up a secondary display? How do I do this? I seem to have a missing 'detect displays' if I press the 'Option' button on my 'Displays' in System Preferences?

I have ADHD so I find this kind of thing very challenging, so I'm wary of messing up my new laptop.

Thanks in advance.