Summarize this article in one sentence.
Position yourself directly between and beneath the rings. You should be able to lift your arms straight up with your elbows slightly bent when reaching for the rings.  Unlike muscle-ups performed on the bar, you don't need to start with your body at an angle to build up starting momentum. Since the rings are flexible instead of rigid, it should naturally be easier to lift your upper body even without the extra swing. It should be noted that performing a muscle-up on rings is more difficult than on the bar. While it’s easier to gain momentum, the rings aren’t stable. Because the rings move it will require you to have more control over your body. Raise your arms and grab both rings, using a false grip instead of a normal grip.   If you're unfamiliar with the false grip, you may wish to practice it before attempting to perform a muscle-up. This grip is important because it removes your thumb and wrist joint from the equation and makes it easier to raise your body higher and transition between motions. To grab the rings with a false grip, rest your wrists on the rings and flex your hands down toward your elbows and pinky fingers. Gradually straighten out your arms and kick your feet out in front of you. You should hang from the rings, relying on your arms alone to support your weight.   Note that your hands should be above your head and spread apart at approximately shoulder-width. When using the false grip, it may not be possible for you to completely straighten out your arms. Still, you should try to straighten out your arms as much as possible to make the next step easier. Use your arms to pull your body up until your chin is at the same level or slightly above the bottom portion of the rings.  As you lift your body up, you should try to draw the rings inward. Draw the rings in close together and close to your chest and body. You may have to point your elbows out to counter the balance of the rings. Lean back just enough so that your face moves behind the rings instead of between. Your head will need to be behind the rings so that you can create enough space and momentum to transition to your dip. As soon as you feel steady enough, lean your shoulders and chest forward. Your shoulders should feel as though each one is rolling over the top of each ring.  During this step, you need to get your shoulders completely over the rings. Doing so will allow you to position more of your weight above the rings, making it easier for you to transition into a full muscle-up. Theoretically, you could pull your shoulders straight above the rings by relying on arm strength alone. But, you need to lean forward so that your weight sits over your hands. Otherwise, you will probably sink back down before completing the muscle-up. As you pull your shoulders above the rings, you'll need to start turning the rings to the outside. Your hands will naturally spread apart to shoulder-width, but do not allow your hands to spread any further than that. Turn the rings so your fingers are facing outward. Turning the rings allows you to lift your body up. While you lift your upper body, you must simultaneously begin pushing your legs down while keeping both fairly straight.  You do not need to straighten out your legs completely, however. It’s best to keep your legs slightly bent at the hips so that your feet remain in front of you. Keeping your feet in front of you can help your balance and keep you stable. If you find it difficult to keep your legs straight, you could choose to lift your knees up to rest in front of your lower abdomen. Regardless of whether your legs remain straight or bent, you need to keep your legs slightly in front of you. This makes it easier for the body weight to shift in a way that will allow you to get behind and over the rings. Use your hands to push down on the rings. Continue doing so until your entire chest and upper arms are above the height of the rings. Once you reach this peak, you've completed a full muscle-up.  Your arms should start straightening out but will remain slightly bent at the elbow. Keep your hands apart at approximately shoulder-width. Note that your chest will also straighten out some, but your shoulders and upper chest should still lean slightly forward. Try to keep your spine straight. You don’t want to allow your spine to curve. Curving your spine prevents you from correctly engaging and building your muscles. Keep your core engaged as well. As you pull into this position, your legs will naturally drop straight down beneath the rest of your body.

Summary:
Stand beneath the rings. Grab the rings with a false grip. Hang from the rings. Pull your body upwards. Roll your upper body forward. Position your legs to help you lift your body. Press down on the rings.