Organizing a challenge allows you to crowd-source the most difficult machine learning problems. It is also an excellent way to learn data science. By following this short hands-on tutorial, you can create your first competition or benchmark-as early as today! In this chapter, we give you everything you need to implement, concretely, your own online competition or benchmark. We do not address other practical issues such as finding sponsors or communicating about the event; this is discussed in chapter 13.