Steps 20 to 23 are simple sinks, but be sure to get the right distances using the references in the diagram. Step 24 is a crimp using existing creases and step 26 is only folding more reference lines. As for steps 49 to 55, they consist in unsinking some hidden paper, then mountain folding twice folowed by a double rabbit ear.
Hope that makes it more clear to you. Good luck with this model as it can become very annoying to do (especially the back plates).