Set Aside Sometime to Update
This isn't a small bug fix update. It's a major system update for your Nexus phone or tablet and you're going to want to take your time with it.
We recommend setting aside some time for the Android Marshmallow installation and download process to ensure that everything goes smoothly. We aren't expecting any major problems but you never know what Android updates will bring with them.
Installation times will vary based on the connection you're using so if your internet is slow, allot some extra time. The file is fairly large and it could take awhile to download.
You'll also want to set aside some time to test the update after you're done installing it. You'll also need to log back in to some apps. So, don't install this when you're in a hurry. Set aside an hour or so to get it all done.