To start, place one chopstick between your dominant hand's thumb and pointer finger. Then, bring your ring finger in to let it rest around your hand's first knuckle.
With the dominant hand still in place, hold the other chopstick like you would a pencil, pinched between your thumb and forefinger and resting on the middle finger.
Once you have a firm grip on your chopsticks, practice moving the second chopstick up and down. Note that the first chopstick should stay in its original position.
Once you master the movement, move on to picking up food — preferably larger pieces in the initial stage. Chips or small pieces of pretzels are ideal for practicing.
A good way to practice is to set up two bowls, one with objects and the other empty. Practice moving the objects from one bowl to the other until you reach perfection.