What happens next?

How to plant arborvitae trees
Plant your arborvitae in fall or spring.
This will give the tree time to adapt in its new climate before the hottest summer months or frosts in winter. If possible, plant the arborvitae tree in late fall or early spring, depending on your preferences.
Because of their height, arborvitae plants do not make good indoor plants and must be grown outside. Choose a spot with full or partial sunlight.