Another novice veg-growing question...

I've prepared some vegetable beds. The soil looks reasonably dark and
rich, but has not had anything much growing in it for a few years, so
I've spread a load of compost onto the freshly-dug beds, which,
hopefully, the worms will take down into the soil over the course of
the winter. I read somewhere that it might be good to add some
nitrogen too. So I bought a box of fish, blood & bone meal. The
question is: When is the best time to apply the stuff? Now? Or in
Spring, just prior to planting? How long does it carry on enriching
the soil after it has been applied? Is there any need to dig it in, or
can you just sprinkle it on the surface and let the rain and the worms
do the rest?

Many thanks,

JD