Insert lawn flags into the soil next to any sprinkler heads so you know where they are during installation and tilling. Spray overgrown areas of the lawn with herbicide according to the directions on the package.
Till the soil with a mechanical garden tiller to a depth of 6 inches. Make two passes over the lawn if the soil is especially compacted or high in clay content.
Spread any soil amendments you want to add over the soil, then turn them in with one more pass of the tiller. Rake the soil surface smooth with a garden rake. Discard any root clumps or rocks that you find.
Unroll the sod and lay the first piece over the soil, starting in a corner of the lawn. Lay the sod in place gently so the mesh does not break. Continue laying the pieces end to end so all edges touch. If you need to trim the mesh around a sprinkler head or other obstacle, cut it with a sharp knife.
Roll the sod with a sod roller. Water the sod until it so too wet to tread on, which will help the mesh break down and help the roots establish.