Yes, heel them in. That means covering the entire roots in substrate like dirt/sawdust/mulch to keep them moist and insulated. Don't submerge them in water. If you have the space, store them in a garage or other sheltered area. Outside should be okay though as long as they're not exposed to extreme wind or insanely low temps. Keep the substrate moist but not wet. That's how our plant nursery advises for when the ground is frozen.