The engine likely has no oil or is severely overfilled. Check the oil level first. The mower ships without oil. Remove the oil filler cap/dipstick and add the entire included bottle. Screw the cap back in and remove the hang tag near the recoil starter that says 'The engine has no oil.'
If that didn't work: White or blue smoke from the muffler indicates overfilling from the factory run-in. You'll need to drain excess oil to the correct level on the dipstick.
Heads up: Never run the engine without oil or severely overfilled. It causes immediate, significant damage not covered by warranty.