Hi Emilia,
Sorry it seems the image is not visible. The basic steps on a Mac are identical to other OSes: Unzip, install Java 8 (or higher) and start the jar either by clicking it or by calling it on the command line using the command:
"java -jar lrmixstudio-2.1.3-CommunityEdition.jar"
Hope this helps (event if I'm a bit late in answering :-))
Kind regards,