Combi boiler - no pressure - no heating or hot water?

I have a Vaillant ecoTEC plus 831 - my radiator was not working and I stupidly bled it dry - my boiler now has no pressure so has turned itself off. I need to refill it and have read the instructions but when turning the two 'keys' on the filling loop until they are loose the water doesn't flow. No idea what I'm doing wrong. So worried cos of the snow and it freezing the pipes and have a young baby worried as her room is sooo cold.