Inspect your existing lawn for weeds, and spray any weeds you find with an herbicide to kill them. Follow the directions on the bottle, which may vary with brand. In general, spray the chemicals directly on the foliage of the weed, and at the base of the plant so it can reach the roots. If you want to avoid using chemicals, use a garden hoe to remove any weeds.
Turn the soil with the garden tiller at a depth of 5 inches. This will break up the soil and make it easier for the roots of the Floratam to take hold. Wait one week.
Lay down a 2-inch layer of organic compost on the lawn and go over it with the tiller, turning it back into the soil at a depth of 2 inches.
Go over the entire lawn with a rake to smooth the surface. If you encounter any large clumps of soil, break them up with your hands. The finer the soil surface is on the first 2 inches, the easier it will be for the sod roots to take hold.
Water the soil lightly the day you will install the sod. Do not water so much that the soil settles and becomes compacted. You can then lay the sod on the soil, making sure that each tile is snug against the previous one.