If you have a Nexus 5, 6, 9, or Nexus Player you can download and install the build to your device from the Android developers page. If you need a little guidance, follow our guide to flash the system files to your device.
According to the Android Developers Blog your device will get an over-the-air update if it’s already running an Android Marshmallow (previously known as Android M) preview.
Why this matters: Getting an early build of the freshly minted Marshmallow will ensure developers can get their apps ready for a final release. There are a lot of new APIs and permissions in Android 6.0, so this August build gives some time to tinker with all the features before Marshmallow gets promoted to a final, public version in the fall.
Derek Walter