Do you want to go back to the ancient egyptian time?
The Ancient Egyptians were known to practice magick and many such practices are recorded down in history.
But that goes even to what you believe in. The Dead Sea scrolls have reports of people who practiced magick. The Bible has reports of people who practiced magick. The early Macedonian period has hieroglypics that give rumor to magick practiced in pre Egyptian time. The early Greeks even had their own spellcasters. Unless you only want to go as far back as the 19th Century or the 18th century. Or medival England.
I know that is not really answering your question but hopefully giving you some pointers on looking it up and determining for yourself how you want to answer your own question.
The answer for that does not exist in this age. Magic has been around for thousand's of years. The very first magic practitioner was most likely an early Cro-Magnon (Cave man). On top of that it would have had to have been discovered before they moved out of Africa and migrated through out the world. In conclusion, There is no way to know who was the exact person who discovered the existence of magic.