Take a look at the scheme below and feel free to investigate in detail.  It shows how the components like EPS-WROOM-32, display, buzzer, and pushbuttons are connected. It also explains how different inputs are accepted and processed by different drivers and how they affect the outputs.    

 Now that you know what each component on the mainboard is, you're ready to build your Chatters 

 Check out the Chatter build guide here: