Fill the tank with about 5 dl of water (a bit less than half) using a funnel.
A funnel can be made with the top of one of the PET bottles and a small tube passed through a hole in the cap.
Clip the Gardena connector of the board on the bottle. Return the board and rocket and push the metal bars into the ground to give the bottle an angle of about 80 degrees.
Attach the pump to the extension connector and pump about 50 times.
Do not over pump or use compressor! Move back several metres and pull on the cord; the rocket can fligh up to 100 metres high ! Operate on a large open field (football pitch, etc.). At take-off everybody should be more than 5 meters behind the rocket.