The combustion chamber filled with oil, the smoke should clear after being run for a while. Replace the air filter if the pleated type, if foam wash the filter in soapy water rinse thoroughly then apply a light coating of motor oil. Work the oil into the foam, squeeze the excess out and re install.

Don't forget to check the oil! Leave the mower on its wheels in storage. To look or work under the deck, always tilt up the side with the carburetor. You'll notice that the oil fill/drain is on the other side from the carb - this is so oil can be drained without getting oil in the intake side.