Answer: Unfortunately you did not include information about where you garden so it is difficult to give you specific advice.
If you live in a region where winters are relatively mild, and the ground is not frozen yet, you could plant them now as long as they have been growing outdoors up until now so they are acclimated to the current weather conditions. Water thoroughly to settle the soil when you plant them and then mulch generously over the root area after planting.
If you live in a cold winter area and the ground is already frozen or covered under snow, or if the weather is very cold and the plants have been sheltered indoors and are still leafy, you would be better off storing them in a cold but protected place such as an unheated garage or possibly a cold frame. (Frosts will not harm them but the soil should not freeze solid. The temperature should be about 40 degrees or colder.) This will allow them to go dormant and experience a winter chilling period. Water just enough to keep the soil from drying out completely and going bone dry. Take care not to overwater as this could cause rot problems. Plant them in the spring so they can wake up normally with the weather.
If you do not have an appropriate sheltered place, you can try overwintering them in their pots outside -- assuming they are already dormant. Place them up against the foundation of your house on the shaded north side. Heap mulch around the containers but do not cover the crowns of the plants. Check periodically so they do not dry out any time they are not frozen. This has worked well for me in zones 6 and warmer.
Good luck with your hostas!
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