If it’s working correctly, it should be as simple as accessing (internal ip) : (port) at (external ip) : (port).
There are a bunch of things that might be going wrong if it’s not working. Unfortunately, I don’t have the skills to help you diagnose the issue!
I love this video. The escalating insanity is wonderful. I once got the Harder Drives music stuck in my head for about 2 days straight.