Shovel out portions of the garden bed, leaving between a 6-inch to 12-inch hole.
Spread about half of the gypsum in the hole. Try to spread the gypsum out as evenly as possible.
Shovel in about half the removed soil, and spread the rest of the gypsum on top of it. After spreading the gypsum, fill the hole with the rest of the soil.
Use the shovel to turn over the soil in each part of the garden bed. You may need to turn over the same spot multiple times to ensure a good mix of the soil and gypsum.
Rake the top of the soil. You need to try to break up the clumps of soil as much as possible, and leave the garden bed as smooth as possible.