I have just got some free horse manure from a farm (I assume it's just
been "laid"! as they have a continual supply). It does have a fair
amount of straw mixed in.

I want to use it for my expanding veg plot (raised beds), and wondered
should I

a) Dig it neat into top soil. If so, should I leave it for a certain
period, and is it OK to leave it in closed plastic bags?

or

b) Use it to start my compost bin? I have a 280 litre bin just
delivered and have heard that you can add manure to compost bin. If
so, should it be added sparingly or can I just throw a load in?

thanks
Ross