how to connect to vesc

Hello, i don't really know how to connect it to a vesc. it says: 
#define RXD2 22 // DISPLAY RX 22 TO VESC TX
#define TXD2 27 // DISPLAY TX 27 TO VESC RX
but what is displat rx22 and tx 27? i have several connectors on my cyd one besides the usb c, on close the the led and another one at the side. can you pls help me. Thanks, sorry if my english is not good. not my first language :)