how do i reprogram a keyless entry keypad?

Hi, I really need help! I just bought a 99 grand am GT the keyless entry doesn't work! I tryed a new batt, I tryed what it says in the owner manual, and I tryed the thing I saw on here about holding the unlock, turning the ignition on and off ect..... It didn't work...... Please help does anyone knw how to program it? I really want my keyless entry to work!

Thanks so much!