No offense but this post reeks of #7 on the How to get help on the Dynamo forums post:
Rather than asking for step by step instructions on how to do your task, try attempting it first. At least come up with a reasonable game plan. It takes effort to learn anything new.
With that out of the way, I will say how I would tackle the problem:
You have a face, and you need the points on the corners. That means you need the perimeter of the face and the end points of each line.
Think through what you need and how you would get that from a within Revit standpoint. Use nodes that sound like it would do what you want in baby steps. Try looking through the Dynamo Dictionary to learn about how to use out-of-the-box nodes. It should at least help you get on the right track.