Make sure that you have a recent version of node, node >= 10 will do. To check your current node version, execute node -v in your terminal. If node would not be installed, I advice you to install nvm. This is a Node Version Manager that lets you easily update your node version. For more information see https://github.com/nvm-sh/nvm
Make sure that you have installed all dependencies npm install.
Afterwards just run npm run dev and go to http://localhost:3000/graphql to open the playground.
The server will now watch any changes and update when needed.
All the exercises are located in the ./exercises directory. All exercises are build in such a way that the solution of exercise n is needed to start exercise n + 1.
Don't worry, if you get stuck you can check out the exercise/xxx branch which contains the solution for that particular exercise.