If you just got the tree and it's been growing inside, I'd keep it in the house until fall. Not sure if it needs a seasonal change to be happy, but if it's an elm, it probably does. I grow tropical bonsai and they are very happy to be inside, and don't need a seasonal change, just a few months outdoors until summer. You may want to keep your tree outside for the winter. Use a humidity tray with pebbles and feed lightly with every watering. Lots of light indoors, stay away from dark windows.