I've made concord grape wine. It's ok. It's not great, but it's decent. The grapes are acidic, and not with enough natural sugar to make good wine. So, I add sugar and water (to help cut some of the acidity). I used to lower the acid with calcium carbonate and malo-latic acid fermentation (MLF) but found that the finished wine was better without those adjustments.
As summersoltice said, Jack Keller has a recipe for everything! His concord grape info is great:
winemaking: Requested Recipe (Concord Grape Wines)
I've used the first recipe with good results!