It's easy to do but most of the videos and Keurig has made it unnecessarily confusing to empty the internal water tank prior to storage.
Just pour out the water and put the tank back.
Just turn it on.
This makes the Keurig believe there is water. I just jam a piece of paper town under the float.
Without a pod in the receptacle, just lift and close the pod lever. Put an empty coffee mug where it normally goes.
I chose the large cup size. And then press the brew button
If it is as empty as it can be, the "Prime" indication will show in the LED screen. If not, repeat steps 3 to 6.