Donít think that your fir will be taken from the wild forest: in Europe nowadays, Christmas trees are grown specifically to be used in winter, and for every tree cut down or uprooted another one will be planted. But remember that they are alpine plants, which do not like an indoor climate, especially in winter.
So if possible you should place your tree outdoors, somewhere away from direct sunlight, so that it can enjoy the winter cold. If you want to keep your tree in the house, try to avoid losing all the needles due to the heat.
Whether it is a tree with roots or one cut off at the base of the trunk, your Christmas fir can survive in the house for a few weeks. It is essential, however, that it does not receive excessive heat and that it gets a little moisture. So if possible position it in a room that is not heated much, or in any case somewhere far from any heat source.
In the pot-holder always leave a little water, and if possible put a humidifier or a basin full of water near the tree, to increase the ambient humidity. If possible also spray the canopy frequently, as long as the lights and decorations placed on the tree allow this.