Click the button under the first light; it lights up white. Then click the "square" button above all of the individual symbols (at the very top of the apparatus); the individual symbol above the first light (the lit one) turns into a square.
Then click the button under the second light, select the diamond shape at the very top, and the symbol above the lit light (the second one) turns into a diamond.
Repeat for the third (square) and fourth (circle) symbols; don't forget to click the button under each of these two symbols before clicking on the thingie above, or it will change the previous (still lit) button. Remember, it's the lit button that will change.
When you have plugged in square-diamond-square-circle, then pull the lever on the left; after a horrific grinding noise, the light should change to green. At least it did for me.