Add eggnog and cinnamon to Ninja Creami container. Stir to combine.
Place lid on container and freeze on a level surface in your freezer.
Remove from freezer and process on the Ice Cream setting. Scoop out and enjoy.
Notes
If your ice cream has a hump after freezing, scrape with a spoon to remove before processing.
I usually run warm water on the outside of the Ninja Creami container for 30 seconds before processing. This allows the outer layer to thaw and get processed into the ice cream properly.
You can make this in the Ninja Creami Deluxe and just use the same amounts, or you can 1.5x the recipe to fit the Creami Deluxe. (Use 3 cups eggnog and ⅜ teaspoon cinnamon).
If you have leftovers, smooth out the top and return to the freezer. You may need to reprocess before enjoying again.
If your eggnog ice cream is too soft after processing, return to the freezer for 20-30 minutes to firm up before scooping.