On the high score table, type "SWAMP THING" for your name and then press 'E'. You can now skip levels with the '+' and '-' keys.
To jump into the editor push the joystick diagonaly up/left, press fire, and press the 'E' key.
Start the game as normal, collect the ship and fly to the extreme top left of the playing area. Disambark from the ship and drive the buggy into the corner. Type "STONKER" and re-enter the ship. Now press 'D' to cycle though the available weapons. Press 'C' to cycle though the levels. When entering a level always position your ship at the top left of the screen. On the second level repeat the above process and type "STONKER" again. You can now fly through walls and if you press 'F' you can hover over the switches and collect them.