Unplug your stove. Shut off the gas valve where it connects at the back of the unit.
Remove the grill plates from the stove burners.
Insert a putty knife under the top panel of the stove at the corner. Pry up to pop the spring clip. Repeat on the other corner.
Lift the top panel of the stove up to expose the burners. Locate the igniter mounted to the side of the burner assembly.
Check the wiring running to the base of the igniter. Make sure it is properly plugged in. If it isn't, unplug the wiring and plug it back in. If the igniter still doesn't work, it is likely damaged beyond repair and needs to be replaced.
Unplug the wiring from the igniter and remove the screw holding it in place.
Fit a new igniter on the burner. Reinsert and tighten the screw. Plug in the wiring.
Reassemble the stovetop. Reconnect the gas valve to the stove. Plug the stove back in.