The microcontroller firmware is a PlatformIO project. The source files are located in the firmware folder.
Installation of PlatformIO is beyond the scope of this document. Please refer to the website to find out how to install PlatformIo for your OS. PlatformIO is dependent on VSCode.
Select File > Open Folder... under VSCode and open the firmware folder.
Click on the PlatformIO icon on the left sidebar. Under Project Tasks, select env:esp32dev