How long do I have to steam a store-bought plum pudding?

I bought a plum pudding at the grocery store, the type that comes wrapped in green cellophane. I'd like to cook it for New Year's Day. I know I have to steam it, but I'm not sure for how long. Also, how do I make a non-alcoholic sauce for the pudding? Thank you for any help you can offer.
2 answers 2