How do you do that in a car? And even if walking, how would you do that all the time without walking backwards or sideways?
This is a little more difficult if you are in a car. But the idea is you find the part of the map you are using, and you want first to fold it so that it is an easy size to hold onto. Most maps fold up naturally, but it can be a bit of a trick to learn to do it so the part you want is on the top.
The next thing is to find where you are on the map, and then you have to place yourself in the same direction as the map. The easiest way may be to look at some obvious feature on the map that you can actually see near you, something like a big hill or a lake, and turn your body in the direction of that feature. Turn the map so that feature is at the "top". So if you look down across the map, you can imagine an ant walking along it in the same direction you are facing will get to the mountain on the map, just as you walking on the ground in the exact same direction will get there.
So - if the mountain is to the north of you, you will walk north across the earth while the ant walks north across the map.
Now, if you need to change direction, what you need to do is turn the map as you turn on the ground. Let's say you are part way to the mountain but now you need to turn and walk along to a pond to the east. You stop, and look at your map, with the mountain to the top. The pond in the east will be a turn to the right for the ant. So you also turn your body to the right. But then you need to change your map. You are now walking toward the pond, so the pond should be at the top of your map, so you must rotate your map to the left.
The thing you are walking towards should always be turned to the top of the map you are looking at.
Now, if you walk out of the part you can see, you need to refold your map. This is what is tricky about car maps, because you are so fast you keep driving out of the part of the map you have open. Ideally you need someone to navigate for you, but it helps to have a smaller scale map for driving and with no one to help you should really pull over when you need to change your map around.