Unzip the file.
Run, build.exe
Wait for 10 minutes as the game compiles. This is a demo engine with leaked files. It will take time to build the game.
When in game, press ctrl+I to spwan a player and a car. Enjoy the game.
Change weather, time and other options by opening a console press "tab" button.
Enjoy. Thanks to romil198 for leaking this demo files.