I overwintered mine in a planter in south facing window. Did not prune. It is now in very good shape.

That type of geranium, also known as cranesbill, is hardy in your zone. I would plant it out in the garden. The leaves will turn coppery red in the Fall/winter. If you do not want it to take over (which in my yard it has a tendency to be a thug), you could plant in a large pot in a sunny location and it should overwinter just fine. It's a hardy beast of a plant.

I have two plants, one each in an outdoor planter. I was wondering more if I should wrap the planters for insulation. I thought small shrubs freeze easier and die when potted as opposed to being in the ground. If you say they are thugs I will see next year how well they grow. They haven’t grown much this first year. I love the fall foliage too. Thanks.

I've overwintered perennials that are hardy in my zone outside, but it does take some care. I pulled the planter right up against the house and when fully dormant surrounded it on three sides by lawn bags stuffed with leaves; also put bags of leaves on top of the planter (it was a big half-barrel). My own carelessness did it one year -- I pulled the leaves off the top because it was warming a bit and it rained...then froze...that cycle repeated and because I didn't put the leaves back on the top, the freeze-thaw ice dam that formed on the crown did it in.

If your plants are smallish, or at least not very large, planting in the ground might be better - it's just less hassle in terms of tending to a potted plant's needs, especially in the spring when they need exposure to light, warmth, and moisture yet protection from freezing and frost kill of tender new growth. Planting in the ground in a plastic pot would work too - then you could just pull it up in the spring and slip the plastic pot inside the decorative one and viola! you're done.