Hello,
You don't put = signs, because you don't assign a value to a define, define's are like aliases, it just replace text by another at compile time
So...
#define ResetCom 1
#define StartButton 2 //Do I want these on the primary and communicate via wire?
#define NextButton 3
But it is suggested to use constants instead of defines:
const uint8_t ResetCom = 1;
const uint8_t StartButton = 2;
const uint8_t NextButton = 3;