How do I prepare a good black soil for my garden?

Get some cow manure and mix it in.

Use compost, manure, peat moss and top soil. Mix with existing soil or replace old soil. Talk to and visit your local nursary for more information about your region and prject.

https://www.planetnatural.com/garden-soil/

There are lots of soil amendment available that can be added and tilled into the existing soil. Keep adding over the years to keep improving. I put leaves over the bed in the fall, sprinkled on some fertilizer and covered with a tarp over the winter. The fertilizer and heat from the sun helped decompose the leaves. Then I tilled in the leaves in the spring.

first and foremost get yourself a good compost bin going,2nd thing is buy your soil some earth worms or red wrigglers( https://unclejimswormfarm.com/order-stuff/composting-worms/?gclid=EAIaIQobChMIt7zAkvuC4wIVAdtkCh0efAbFEAAYASAAEgJmwvD_BwE is good place)----organic matter in the form of finished compost, natural wood mulch or shredded bark, leaf litter, mushroom compost, worm castings and more.

So why does organic matter work so well for both soil extremes? The answer lies in the living network of soil organisms that develop in this mass of biodegradable goodness. The very organisms that break down the raw material into soil particles are the ones creating the ingredients that allow these particulates to bind together in various sizes. In turn, they create pockets of space for air and water to collect and move, and for roots to more easily expand.here is great info. https://joegardener.com/how-to-improve-your-soil-3-simple-steps-for-making-any-soil-better/ don't use any pesticides,soaps,salt or vinegar or herbicides; these all change chemical balance of soil & kill off beneficial microbes needed to maintain a healthy organic soil which is key to healthy plants. Live Lady bugs,Praying Mantis egg cases,Green lacewings and Live Nematodes in the soil with the earthworms. Another great site https://www.arbico-organics.com/