You seem to have visited github.com/me50/USERNAME, but you forgot to replace USERNAME with your own GitHub username! For instance, if your GitHub username were jharvard (which it isn't!), you should have visited github.com/me50/jharvard instead of github.com/me50/USERNAME.
Visit github.com/me50/USERNAME, where USERNAME is your own GitHub username, not USERNAME literally!