First, you must figure out how to escape the room. There must be a key somewhere. Carefully observe your surroundings, search through furniture, and examine the contents of drawers. You will have to do this quite often, so start getting used to it now. There are plenty of rooms like this in the house, and each one has something necessary for escaping. Only by collecting all the necessary objects will you be able to turn off the alarm and unlock the main door.
WASD - Move F - Use Shift - Run Space - Jump