You will need the specifics to do it right, but here's the overview;
Buy a starter culture or a bottle of raw kombucha tea.
Keep everything sterile.
Make some fresh tea using black tea, and add white Sugar
in the proper amount.
Cool off tea to room temperature. Pour in glass container.
Add the starter culture.
Put a screen or cloth on the top so that it can breathe but stuff can't fall in it. Put it in a dark, medium cool, quiet place.
Let it sit for a week or two. Check on it.
At some point, it's ready to go, and you'll take make some more fresh sweet tea, take out the big weird culture thingy from the first batch and put it in the new tea.
Store and drink the first batch of tea while the 2nd is fermenting.
It's a cycle you repeat over and over.