There are a few ways that you can modify a chest fly exercise to make it easier or more difficult, depending on your fitness level. If you're new to working out, you can start with dumbbells that are five to 10 pounds each. As you get stronger, you can increase the weight of the dumbbells. You can also modify the angle of your body in relation to the floor. If you're doing a standing chest fly, for example, you can lean forward slightly from the waist to make the move harder. Or, if you want an easier version of the move, you can do it sitting down on a bench or stability ball.