Each valve has three rings. Leave the ring nearest the canvas alone. Undo the middle ring to let air out. The outer ring is a one-way valve for inflating.
The three rings
Nearest the canvas: attaches the valve to the tent. Leave this one alone.
The middle ring: undo it to let air out and deflate the tent. Make sure it's done up before you inflate.
The outer ring: a one-way valve for inflating. It won't let air out.
Why three valves?
The tent has one air tube but three valves. You can inflate from whichever valve is easiest to reach, and when you deflate there are three exit points, so it goes down faster.
