Your mower was shipped without oil. Running it dry will seize the engine.
Add the entire included bottle of oil to the engine. Screw the filler cap/dipstick back in. Remove the hang tag near the recoil starter that says the engine has no oil. Pull the starter grip briskly.
If that didn't work, check the blade control lever. You must pull it back and hold it against the handlebar while pulling the starter. Also, turn the fuel valve to the ON position.
Heads up: White or blue smoke from the muffler after adding oil means you overfilled it. Use the dipstick to check the level.