Slide the card under the clear grid, then place the red gear and yellow wheel as indicated. Each puzzle will show you an array of color and sizes of gears, and how many of each you'll need (you'll see them printed along the bottom of the card). Pull those out (you MUST use all of them!).
The next step -- solve that puzzle!
Crankity is a great brainteaser of a game best for ages 6+ years.