You really just need a SCOBY. That’s a Symbiotic Colony Of Bactria and Yeast. It’s like a floating disk that ferments your tea into Kombucha. Lots of helpful videos on Youtube. You can buy a SCOBY or you can make one from scratch using a bottle of store-bought Kombucha:
https://www.youtube.com/watch?v=BUqvSz4p3fw
Thank you.