it needs time to integrate and stabilize the soil. Apply two to three weeks prior to planting.
you can mix compost into your soil without a lot of back-breaking-work! Spread it over your garden ( late fall), after all, your harvesting is done. simply Cover with a winter mulch, hay or chopped leaves and let nature take its course. the melted snow and organisms in the soil will have worked the compost in for you by spring.