Take a look at the scheme below and feel free to investigate in detail.

It shows how the components like EPS-WROOM-32, display, LED matrix, SD sloth, encoders 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 Jay-D. 

Check out the Jay-D build guide here: