Even though Egyptians didn't have any good technology at that time they would build pyramids by cutting and moving pieces of stones and making it into a pyramid shape. We still don't really know how they did their work but the stars were a guide for them to use as math and calculate where which of the pyramids corners would go.
(Hope this helps, I'm not so sure about the stars part but I saw it on a history channel a while ago. Good luck!)
