There is a lot of confusion over the name 'Geranium'. There is a genus Geranium and there is a related genus Pelargonium. The confusion arises over people calling Pelargoniums Geraniums in common parlance. If yours were definitely hardy Geraniums there was no need to take them indoors. That treatment is for Pelargoniums which are not hardy. Hardy Geraniums need no care to speak of. They will reappear in the Spring as you have seen. If you get drought they might need some water. If you want to do something with them you can trim off dead flowers or even trim them right back when they get a bit ratty and they will push out fresh new leaves. But essentially they are almost zero maintenance.

Here is a link that might be useful: Examples of hardy Geraniums.