To hid you must approach an area in a room that is highlighted. Your bed for example is an area you can hide behind. To create more areas, you must walk into a room with the light turned on and wait. If your eyes close, wait a few seconds and you will create something for that room. Leave the room and return and you can create some more stuff for that room. If there is a highlighted object, then you can hide behind it.
If your eyes don't close when the light is turned on, then you probably can't create something for that room. Now all you need to do is wait for a monster to enter the same room you're in (you should already be hiding) and hope it doesn't spot you.
This is only available every other mission. When you look at the map between each level, they are the levels with the eyes (not the house shape levels).