What is this brown goop on my new bike frame?
It looks like cosmoline  which is a waxy rust preventative. It can be difficult to remove from finished parts without damage to the paint. If you can, scrape some of the heavy stuff off with something like a plastic knife. Then I would try something like WD-40. If it doesn't soften it right away soak a rag and wrap it around the fork tips over night. You can see if a hair dryer will soften it without hurting the paint