Hello,
First of all, don't worry about viruses if you download the game from our page. We guarantee we haven't added any virus to our game 😄
Then, To install an app on a Mac,
- Open the .dmg (it might open a loading window to check the file, you can hit the "ignore" button
- A window with the game on one side, and the "Apps" folder on the other will appear
- Drag and drop the game on the "App" folder
- Wait until it's over
- The game is now installed. you can leave the .dmg, go to your apps and launch the game.