I keep my in a room under hanging lights. You should prune it back a little before bringing it inside. Make sure the temperature is above 70 degrees. This is how I do it. Hope this helps a little!
Mike

I live in Tex/Z7. The white comes back from the root AND reseeds its self like mad. Other colors don't come back from roots but reseed profusely. Any of them transplant very well when about 3" to 4" tall.
And there's always plantings from all the seeds they produce. However mine are planted directly in the ground.
I wish you good luck with the over winter.