This version has been designed to make programming easy. As such you should be able to use a standard USB to Serial adapter with the following pinout (this is a common one on eBay)...
GND (NC) 3.3V TX RX (NC)
Once you've set up the ESP32 toolchain (http://esp-idf.readthedocs.io/en/latest/get-started/) you'll need to set the correct serial port for your programmer. Do this with...
cd Firmware
make menuconfig
And change the Serial Flash Config -> Default serial port setting. Then to build and flash just run...
make flash
To put the board into programming mode, hold the switch attached to Program down while pressing the switch attached to Reset.
Most ESP32s seem to come with a WiFi updater pre-programmed so it might be possible to removing the programming requirement but I haven't had time to look into this yet.