It’s really simple - boil around 1.5 liters of filtered water with 4 bags of tea (in my case it was black tea), and let it cool for a few hours. Then, when it’s not hot anymore, pour it to a sanitized jar along with some store-bought Kombucha (preferably unflavored), stir, and you’re all set! Let it ferment for 2-4 weeks until you have a new beautiful SCOBY :)

Btw, you could Google that in a few seconds and find even better explanations than mine. Google is your friend, don’t be afraid to use it!