Check that the battery is not empty. Battery may have got empty in the sales package and the phone does not start at all when the power button is pressed for the first time after unpacking. If this is the case, you need to charge the phone before it can be started.
Note that when the charging starts, it may take several minutes before anything is seen on the screen. If nothing happens, disconnect the charger and try again.
To see if the charging works properly, check if the charging indicator on the left side of the phone (above the Micro USB connector) is lit or blinking. If the charging indicator is lit or blinking, the device is properly charging.
If nothing happens and the device doesn't start up, try resetting the device by pressing down the power key for about 8 seconds.
If the charging indicator light is still not visible and the battery can’t be charged, the phone should be taken to Nokia Care point for repair.