When to add compost to your garden
With homemade, fully decomposed compost, the nutrients are more readily available to plants and can be added onto just-planted garden beds or soon-to-be-planted garden beds. For many urban growers, bagged compost is what is easy and available. If you're using bagged compost, add in layers about 1 to 2 inches thick in early spring. Now (early March) is a great time. Dig in lightly with a bow rake, and leave the compost to rest a week or two before you plant seeds or starts.
When using homemade compost or if compost is thick with green matter and fibrous, add to garden beds in autumn. (You should also allow chicken manure some time to cure and age before seeding or planting directly.) The compost will be mostly decomposed by spring and beds should ready for planting. With backyard compost, get into the practice of adding 2-3 inches of new/fresh compost in the autumn (in lieu of cover crop) so that the compost can decompose over winter and into early spring.