@fatdollar You just forwarded port 3000 from the host to port 3000 in the container but the getting-started container listens on port 80 which is the default port of nginx not port 3000. @logixx forwarded the host port to the right container port. The port on the right side is always the container port.
docker run -dp 127.0.0.1:3000:80 getting-started
The above command should allow you to access the webpage from the browser on port 3000.