I just tried to make wine for the first time. Manderin oranges, sugar, water, yeast, tea for tannin the whole kit and kaboodle! In a rush, I forgot to add the Campden tablet prior to doing all this and just added it after mixing all my other ingredients together. Did I just mess up my whole batch of wine, or Will this ferment? And please be clear. Do I add the tablet before or after the wine is finished?
The Campden tablet is used to remove wild yeast from the wine "must" (juice), so the only yeast fermenting the beverage is the one you add. If you add it after the yeast it will kill or severely inhibit all the yeast.
It's likely that the introduced yeast will out-compete any wild yeasts in/on the Mandarin Orange juice. If not, it should still be OK. You might just get some extra subtle flavour differences. If you made a ginger-beer via a ginger "beer plant" or "bug", these are exactly the wild yeasts you're fermenting with, so I don't think it's a big deal.
Normally the Campden tablet is introduced 24 hours before the yeast.