What is the method for sincere repentance after kissing a foreign woman on the mouth and vulva without penetration?

What you have done is an ugly transgression, so you must make sincere repentance by abandoning the sin, resolving never to return to it, and regretting having committed it. If your repentance fulfills these three conditions, then it is accepted, and Allah will erase the effect of this sin from you; for the Prophet, peace and blessings be upon him, said: "The one who repents from a sin is like one who has no sin."