If you do not do this nothing will happen when you try to play music. Now you need to configure spotifyd to use your Spotify premium account. But you can also build yourself from the source code provided by the spotifyd GitHub page. Installation for Mac OS is easiest done through Homebrew.
For Linux and Windows, please see the official documentation for spotifyd and spotify-tui. This tutorial is mainly focused on how to get Spotify working in the terminal on Mac OS machines. Follow the simple steps and you will be up and running in no-time. Run Spotify in your terminal application instead of managing a tab in the browser or a resource-hungry desktop application.