Pull the damaged panels completely off the garage door. A hinge on both sides of the frame holds the panel in place. One side already may be detached if the panel was popping out previously. Loosen any additional bolts or screws on the panel with a wrench or screwdriver and slide the panel out of the rails once it's loose from the hinges. You may need to remove several panels to get to the ones that require repair, depending on the design of your door.
Examine the panel and the frame on the door to check for warping. This is especially likely if the door was struck by a car or received some other hard impact. Correct any small dents or bends in the frame with a rubber mallet. If the panel itself is highly warped, replace it with a new one of similar size and insulating value.
Slide the new or corrected panel back into the frame and reconnect it to the hinges on both sides. Tighten down the bolts again with the wrench.
Test the door by opening and closing it several times to verify the new panels fit and move correctly.