1. Open the hood of your Subaru.
2. Remove the decorative engine cover by unclipping the retaining clips and lifting the cover off.
3. Locate the spark plugs along the top of the cylinder head, near the front of the engine. They will be arranged in a row, with one spark plug per cylinder.
4. To remove a spark plug, disconnect the electrical connector and use a spark plug wrench to loosen and remove it from the cylinder head.
5. Check the condition of the spark plug and replace it if necessary.
6. Tighten the new spark plug by hand until it is snug, then use a spark plug wrench to tighten it to the manufacturer's recommended torque specification.
7. Repeat steps 4-6 for the remaining spark plugs.
8. Reconnect the electrical connectors and replace the decorative engine cover.
Note: The location of spark plugs may vary on some Subaru models. It's always a good idea to consult the vehicle's owner's manual or a repair manual for specific instructions.
