Browse the store for a game you want to download.Go through the necessary steps on the screen.Tap Create New Account or Log in into an existing account if you have one.Launch Steam from the Applications folder.How to download a Steam game onto your Mac Drag Steam into the Applications folder.Double-click on steam.dmg to launch the installer.Depending on the browser, this may open automatically when the file finishes downloading. Click Install Steam at the top right of the webpage.In case you haven't installed Steam on your Mac already, here's how.