The update will take some time to reach all devices, if you haven't received a notification yet, just head over to Settings > About phone > Check for updates.
In a time when most manufacturers and carriers too are working to get Android Nougat on smartphones, AT&T's Marshmallow update is arriving a bit too late. But is still a welcome update as you may get better battery life with Doze mode and better performance as well.
If you have updated your Note to Marshmallow, we would love to know your experience. Hit us up in the comments below.