z-stack mesh - add a new input

Hi there

I defined SW_7 as below in hal_key.h :

#define HAL_KEY_SW_7 0x40  // Button S2 if available

now I have 2 questions

1)what PORT and PIN are non-used in generic application or I can use for this aim?

2)what changes do i need to  apply in hel_key_c for modifying  codes?

with the best regards