Reading an analog clock when the minute hand points to 12: the hour hand tells the hour (1 o'clock, 2 o'clock, etc.). Understanding that the hour hand is shorter and the minute hand is longer, and what position means '12,' are key.
An analog clock has two hands, and the first thing to learn is how to tell them apart. The hour hand is the short, stubby one — think of it as the "lazy" hand that moves slowly. The minute hand is the long, thin one that races around. When you want to know the hour, you look at the short hand; the long hand is your signal for whether it's exactly "o'clock."
When the long (minute) hand points straight up to the 12, that is the signal that a new hour has just started. At that moment, the short (hour) hand is pointing directly at a number on the clock face — and whatever number that is, that is the time. If the short hand points to 3 and the long hand points to 12, the time is 3 o'clock. If the short hand points to 7 and the long hand points to 12, the time is 7 o'clock. The minute hand at 12 is your green light to read the hour hand directly.
It helps to remember that there are 12 numbers on the clock face, and the short hand visits each one in order: 1, 2, 3, all the way up to 12, and then back to 1. Each visit takes exactly one hour. By practicing reading clocks set to different hours, you build up the habit of first checking the long hand (is it at 12?), then reading the short hand to get the hour. This two-step check — long hand at 12, then read the short hand — is the foundation for reading half-hours and minutes later on.