Allow the stove to cool, remove the top grates and lift up the stovetop (like you would a hood of a car) to expose the burner piping. On most stoves, the air shutter is just behind the burner gas valve. It is a sliding plate or tube that covers the burner air vent. Loosen the set screw that keeps the shutter from moving. Turn the burner on fully and slowly open the shutter until the flame turns blue. Retighten the set screw, turn off the burner, lower the stovetop and replace the top grates.
Here's a DIY guide on how to clean the burners and grates of a gas range: searspartsdirect.com/diy/article/how-to-clean-grates-and-burners-on-a-gas-cooktop-video
For more specific help, as the question again with your full model number. You can go to SearsPartsDirect.com and enter your full model number for schematics and parts, such as new burners, for your Kenmore range. For a repair, you can call Sears Home Services at 1-800-4-MY-HOME.