There is some good information on this site:
I had no idea there were so many ways to over winter these until you asked your question. Thanks I just learned something too!
I wish I had known about this earlier. I tossed mine and now I'm sad. But I'll know better next year! Thanks for posting this question.
This method sounds interesting and works well for the presenter, although I have never overwintered them, it sounds doable:
All fantastic info here! Do you know what Zone you are in? I am in zone 9 and mine are perfectly fine in ground year round. Here is one of them. Even blooming in January.
This may help: https://homeguides.sfgate.com/winter-care-container-geraniums-71654.html