Did they roll it down to ensure good contact between the bottom of the sod and the top of the soil? If not and they did not promise to do that, you can either rent a roller or walk it yourself. Grab all your neighbors and line up. Everyone walk in baby steps over the entire surface to press the sod down against the soil. Even children can help with this. The weight per square inch of foot surface is just right for doing this.

Water for a few minutes (5-15 depending on your sprinkler), 3x per day (breakfast, lunch, and dinner) for the next 2 weeks or until it is knit down. The idea is to keep the surface of the underlying soil moist, NOT SOGGY, until the roots grow down. If, after you water it, the sod sinks down into the soil when walked on, then you watered waaaaaay too much.

After it seems to be knit down, then mow it down in increments over a weeks time until you get to the mower's lowest setting. You might scalp it every time you mow, but that's fine. It is bermuda after all.

If you don't already have a good soil test telling you otherwise, then fertilize with a starter fert at the bag rate after the second time you mow. You want to make sure the roots are working before you fertilize.

On a small scale you can start sanding any time. Over the next few weeks some of the soil stuck to the bottom of the sod will melt down and onto the soil underneath. That will take you into late April. I might wait and evaluate where the low spots really are until May. You can pre locate them with sprinkler flags (wire things with flags on them) so you can find them later. You can use topsoil for small scale leveling and filling holes. The problem with topsoil for large scale leveling is dragging the clods around with the drag. For filling holes you will use a lot more sand or soil than you might think. It needs to feather out to match the grade of the surrounding soil. Holes do not look like a putting green hole. They gradually slope down and up taking up more volume than it seems.