No, you need to buy one with roots. But check that the roots haven't first been put into boiling water to check them. If you want a tree you can plant out into the garden afterwards, you'll need to keep the roots very moist, preferably in a pot of moist soil during the time it is indoors, and limit its exposure to dry central heating.
If a rooted tree is completely bare (i.e. not covered in electric lights) it will help to mist it daily with water, but please don't do this if you if you have any electric lights on it as this is dangerous. A tree with a cut stump will start to die and shed its needles fairly soon after bringing into a warm centrally heated environment.