How do you tell which side of the contact lens to put on?

Should be bowl shape. In general, the soft contact lens will have correct orientation when the unit is opened. Try to maintain that same direction without flipping. Otherwise, set the lens on the tip of the finger and look at it from the side/edge. The way that makes it look more like a bowl is correct. If it looks more flat at the edge like a saucer/plate it is inside-out. Also, a reversed lens is less comfortable.