you need the medicine kit, i forget where in dammek's house it is but it looks like a monster bag sort of thing. you also need the guidebook on all the alien stuff. you need to heal his lusus, the game will prompt you to read about it and then you can use the medicine kit. the lusus will allow you to ride it then and you'll leave the house.
I don't know where you are, so I'll just walk you through the whole thing. Get the milk from the fridge and then the bowl from the cabinet on the right hand side. Put the milk into the bowl. Put the bowl in front of the kitchen door and let the lusus have it. Go upstairs from the kitchen. Get the green bag that's on the couch in the back of the room- you'll need it later. Grab the hoverpad and use it to remove the junk blocking the stairs on the far left. After that, go down the stairs and snag the book in the front left hand corner, then go through the door that you energized with the green cube earlier. Keep going left until you're in the room with the lusus in it. Use the book on the lusus, then the green bag. A cutscene will trigger. Click on the lusus, click "RIDE", and go through the chat box and last cutscene that happens before you leave.
What you need to do is click on the antler of the deer. Then click on the tiger and you should switch to Jude. Look at the poster in the bottom right, then his desk drawer, then click on the pigeon. Repeat three times.