Hi thank you for your message! Normally when you download a game from Mac that is not from the apple store the OSX don't let it run.
Once the rar is unziped (or unrared?) double click on the Sol705.app (the one with the logo of the two characters) file and then go to System Preferences. Then on Security & Privacy - General be sure to Allow apps dowloaded from Apps Tore and Identified developers Open it anyways. It should work unless you have an very old mac.
If not let me know. The other possibility is running from Steam also for free after instal the Steam manager.
Hope this helps!
