How to download un 4.15.1 on MacBook Pro?

How to download un 4.15.1 on MacBook Pro ?

Hello. You can download 4.15.3 from Epic Launcher (minor versions are the same except bug fixes).

If you need 4.15.1 and nothing else, you can download if directly from github (you need to be logged in I guess):
https://github.com/EpicGames/UnrealEngine/releases/tag/4.15.1-release

and you will be able to build editor using this source code.