The short hand shows the hour. The long hand shows the minutes.
Count the long hand in fives. The 1 is 5 minutes, the 2 is 10, the 3 is 15, all the way round to the 12, which is 0 or 60.
Say the hour, then the minutes: 6:25 is 'six twenty-five'. A.m. is before noon and p.m. is after.