In American English, people would ask, "How did you find me?" when asking someone how they located you, for example:
"How did you find me? Did you use Google Maps, a Navigator app, the telephone directory?"
In American English, it would only be a very unusual and specific reason for asking, "How have you found me?" An example might be: "I am finished with the interview for the job. How have you found me? Do you find me qualified to start work, or do I need additional job skills?"
As you can see, it would be really unusual in American English to use "How have you found me?"