how long after the first interview does it take to get the results??
Between a week and two weeks, depending on when in the interview cycle you were seen.
how do they notify the candidate?
They normally tell you to ring on a certain day (the Friday a week following the end of the interview blocks by memory). Sometimes you get rung before hand - but it does not mean that you have not been successful if they haven't rung you, so don't panic!