The G-spot area is a zone on the front wall of the vagina, the side toward your belly. Just inside the entrance, on that upper side, the skin feels slightly rougher than the smooth walls around it. That rougher patch is what is usually called the G-spot area.
It is not a button. Behind that wall lie the urethra and the spongy tissue around it, closely connected to the inner parts of the clitoris. Some researchers describe all of these as one linked group of tissue. That is why touch there can feel like several things at once.
What women feel there varies a great deal: deep fullness, an urge to pee, not much at all, or a mild ache. None of these is wrong, and there is no single map that fits everyone.
Finding it. With a finger or two inside, palm facing up, curl your fingers toward your belly in a come-here motion. Just past the entrance, your fingertip will often meet the rougher patch. If you do not feel a distinct patch, that is normal too; bodies differ. Resting your thumb on your clitoris at the same time helps you find it.
When. The front wall usually feels better once your body has opened with arousal (see Wet is not the same as ready: how arousal opens the vagina). Before that, touch there is more likely to feel like an urge to pee than like pleasure.
How. Pressure, rubbing and the two together all work; see Touching the front wall: pressure, rubbing, or both.