In a dream you can talk with a camel, fly past your old school and meet someone long dead. None of it seems odd. Only on waking does it seem strange. Inside the dream you assume, as you assume now, that this is ordinary life.
The second practice works on that assumption. Several times a day you stop and seriously ask: Am I dreaming? Then you test it. Habits made by day carry into sleep. Ask often enough, and one night you will ask in a dream. The test will fail, and you will know where you are.
The asking matters more than the test. Most people ask lazily, already sure of the answer. That habit carries into the dream too: they jump, expect to fall, and fall. So ask as if you truly might be dreaming. Look around. How did you get here? What happened just before?
Then test, expecting it to work. Pinch your nose shut and try to breathe through it: in a dream you still can. Or give a little jump with the intention of floating. In the body you land. Outside it you float.
This is the door question from page 5, carried into the night.