Just bought new MacBook, best way to install my purchased Scrivener 3 on it without transferring from old Airbook

Maybe it’s easier than I realize but it’s late and I’m tired, ideas?

Download and install. Either from this L&L site, or from the Mac App store, depending on where you bought it.

Installing an application on MacOS is usually very simple. What can take a bit longer, and will depend on the complexity of the application, is configuring all the preferences to suit the way you want to work. In particular, it is worth taking time to make sure that settings for backup files and the like are configured as you want them. That can save a lot of trouble later.

If you have old projects saved on the old laptop, you will need to transfer those to the new one either by using something like a USB stick or external hard drive, or by saving them to a cloud service that you can access from the new laptop. If you do that, it is worth zipping the projects before you save them to the cloud service, unless you want to use Dropbox for sync with another device, in which case you should read the instructions about how to do that.

I downloaded Scrivener on my new Pro and found my license key in my email and entered it, presto.

I just needed a second wind of brain power last night, thanks for the responses though, hopefully someone sees this one day and all their brain needs is the cue. The thought and anticipation of what I was going to have to do was worse than actually doing it.