If you slide the first two fingers of your Hand, pads of fingertips facing up, into a well lubed woman, slide in to the second knuckle. Now, curl your fingers straight up and back, as if you are doin the "come hither" gesture, ironically.
at that point you should feel, with your fingertips, a slightly raised and rough, circular area. It would also be located where if the clit. From outside the body was connected to the interior wall of the vagina.
Steady, strong pressure, not usually stroking, particularly combined with oral sex is great for a lot of women. She will know that the spot is right because even if she just emptied her bladder, pressure on this area will make her feel as if she still wants to pee. Not so. Her body is actually gearing up to ejaculate.