Adding flags in CodeBlocks compiler

Question

I'm writting a program with POSIX semaphore usage in CodeBlocks. So it can't compile even a such code :

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>

int main()
{
    sem_t a;
    sem_init(&a, 0, 3);
    return 0;
}

But using terminal and flag -lpthread, everything works.

gcc main.c -lpthread

So, how can I add this flag to compiler?