Learn a proper false grip with the heel of the palm (little finger side)on top of the ring...and perform lots of chin ups maintaining that false grip. Eventually you will find the false grip will allow for a proper transition from below the rings to above...then, just work lots of dips and eat two or three more plates of spinach for dinner
Aside from the spinach which probably the best advice haha you can try doing L-muscle ups.
If you have a set of adjustable rings, place yours feet on like a spotting block so that you can hang in a false grip of the rings with your legs on the box. So you are like in a L-hang. From there you can work the muscle up and used your legs to help yourself a little bit if need be. This can be sometimes a good intermediate step between muscles by yourself and with some help.
Otherwise yeah pretty much what was said before. Work on doing fast explosive chin-ups, dips, and work the transintion phase with a spot.