How do I make plum wine?

My wife happened to be at the Haymarket at closing hour Saturday. One vendor selling green plums decided he didn’t want to cart the unsold fruit home. He sold off whole 20-pound (9.07 kg) boxes of plums for a buck a piece. She couldn’t resist getting one. Now to figure out how to make wine from it. And I do have a cellar to ferment it in.

Do I need a gallon demijohn or can I improvise? How much sugar do I need to add to get a reasonable alcohol content?