If you have a compiler that supports C99 you can
#include <stdbool.h>
Otherwise, you can define your own if you’d like. Depending on how you want to use it (and whether you want to be able to compile your code as C++), your implementation could be as simple as:
#define bool int
#define true 1
#define false 0
In my opinion, though, you may as well just use int and use zero to mean false and nonzero to mean true. That’s how it’s usually done in C.