Literally, Xcode -> New Project -> macOS -> Document.

Gives a full document-based application shell written in Swift and SwiftUI.

That said, you might try reading macOS Programming for Absolute Beginners, but honestly the world's been turned upside down by SwiftUI recently, and you'd be better off starting there.

Swift and SwiftUI give you access to iOS, macOS, iPadOS, tvOS, and watchOS.

Head over to Ray Wenderlich's site and grab a couple of his beginner books.