Installing Software From DMG Files
There are several ways downloaded software can be installed on a Mac. One way is by downloading a DMG file. A DMG file is basically an application compressed into a smaller package, so downloading is faster. A DMG file can have the full application in it, or an installer.
Here are the steps for installing an application from .DMG files on your Mac OS.
1. Download a .DMG file on to your Mac computer.
2. Open the file by double-clicking on it. A new icon having a same name as the downloaded .DMG file appears on the desktop.
3. A Finder window should appear automatically; if it doesn’t, double click the new icon to open it.
4. In the Finder window, locate your application’s icon and drag it to your Applications directory. Once you have done this, your application is installed.
If a particular application doesn’t provide a shortcut icon to the Applications directory, you will need to open up a Finder window. To do this, press Command + N and then drag and drop the application’s icon onto the Applications directory, which is shown in the sidebar. You can also open your hard drive and navigate to the Applications folder that way.
If the DMG file does not contain the application, but instead has an installer for the application you will have to run the installer. An installer icon typically looks like an orange open box. To install from an installer follow these steps:
1. Double click the icon.
2. If there is a license agreement, you'll want to agree to it (or not, but then you won't be able to install the software). You can read the agreement, if you choose.
3. You will be prompted to pick an installation location. This is usually defaulted to the Applications folder. You can decide to pick a new location, or just continue.
4. You may or may not be prompted to type an admin password at this point. If you are, do so. If you aren't the application will install and you will be informed when finished.
5. Close the window when finished and you can run your application.
Once your software is installed, it is good to clean up the things you do not need now. Here are the steps you can follow to do the cleaning:
1. Close any open Finder windows.
2. Eject the application’s disk image. Click on its desktop icon and then press Command + E, or drag that DMG icon from the desktop to the trash.
3. Delete the application’s .DMG, or save it as a backup.
As you can see, installing applications from a DMG file is very easy. Of course, with the introduction of the Mac App Store this process is going to become less used.
Resource: Author's own experience