Once you double click the DMG file it will open as a read only drive and appear under devices, if you then click on the read only drive it has opened as there will either be a .pkg file you can double click which loads an installer menu.
If however it is just a single icon or program on it's own, then you need to drag (or copy and paste) it into the applications folder on the computer.
2) Open the terminal/console and enter the folder. You can do it easily by writing §cd § and drag-dropping the folder to the terminal and hit Enter.;; 3) Write §shasum -a 256 -c LibreOffice5.2.2MacOSx86-64.dmg.sha256§ and hit Enter. The dmg file download wont open in mac sierra please help. Is it just that.dmg that won’t open? Have you tried a different one to compare? Basically there’s no reason that should be happening. So unless it’s happening with other.dmgs, I would say something is wrong with that one. Open the folder 7-Zip created to browse the contents. Although this won’t help you do much with the actual content within the drive, you can use 7-Zip to view the content within the disk image itself. If 7-Zip struggles to extract your file, try right-clicking and using the Open Archive option. Convert a DMG file into an ISO. I'm using Audacity version 1.2.5 on a Mac OSX version 10.6.5, and I have a couple of important AUP files that won't open. I didn't realize at the time that I should have saved them as WAV files and not changed their location on the computer. I tried moving them back into the folders they (likely) were originally saved in, but they still won't open.
Once it has finished copying, you can then eject the mounted read only drive image.
.dmg Won't Open
Additional instructions here; http://www.howtogeek.com/177619/how-to-install-applications-on-a-mac-everything-you-need-to-know/ High sierra dmg full. https://hwbxza.weebly.com/blog/ios-84-jailbreak-download-mac.