Arrange gems so that 3 or more of the same color are touching. Click and hold a gem and then slide it. When the gem is where you want it, release the mouse button to make a match. As you match gems, the jewelry-completion meter will rise. When it reaches the top, the jewelry is completed and will be sold to the current customer.
Special tokens allow you to upgrade your shop with more jewelry and customer treats. Customers become unhappy while they wait (as indicated by the heart-meter). Keep them happy by making matches and giving them treats. Happy customers pay more for jewelry!