If you want to test an iOS beta or developer preview on your iPhone or iPad and you are a Windows user, you can now do that by extracting the IPSW from the iOS beta DMG file with the help of the DMG Extractor software. All you need to do is to download the DMG Extractor and have the iOS beta DMG at hand.
After extracting the IPSW file from your iOS beta DMG file, make note of your IPSW file that you’ll be needing to upgrade your iPhone, iPod or iPad device.
To upgrade your device to the iOS beta: open up iTunes, Click Shift and choose "Restore" and select your iOS IPSW file that you extracted with the DMG Extractor. Read more about how to upgrade your iPhone, iPod or iPad to iOS Beta.