pd.....excellent information source.
redneck.......anytime can be a good time to add manure, the issue is what type you have available and in what quanity.
the information source pd supplied is a good reference, take a look at it and use it for a beginner's guide.
It's not too late to add animal manure as long as it is a light application, I would incorporate deep into the soil.
If it is well composted a year or more, you can be generous in the application.