Here are the instructions per your owners manual. If all else fails, go back to the manual ... you can almost never go wrong by doing so, especially if you still have warranty left on your vehicle.
NOTE: I'll throw some descriptive stuff in along the way to clarify things a little. What @rviertel has written is fairly good, but I have some contention with a few finer points.
- Warm up the engine by letting the engine idle for approximately 10 minutes to ease draining the engine oil.
- Park the vehicle on a level surface and turn the ignition switch to the "LOCK" (off) position.
- Remove the oil filler cap.
- Drain out the engine oil by removing the drain plug while the engine is still warm. The used oil should be drained into an appropriate container and disposed of properly.
When you are ready to drain the oil, jack the vehicle up and support it, using a jack stand if you have it. For safety reasons, it's not prudent to go under the car with just a hydraulic jack holding it up as it can fail at any time. If you don't have your car slammed to the ground, there may be enough ground clearance to drain the oil without jacking it up. If so, this would be far easier than any other method I can mention (I can do this with my truck).
- Wipe the seating surface of the drain plug with a clean cloth and tighten it securely with a new sealing washer after the oil has completely drained out.
- Remove the oil filter with an oil filter wrench.
- Before installing a new oil filter, apply a thin coat of engine oil to the seal.
When applying a thin film of oil on the filter seal, ensure you use clean oil.
- Clean the rubber seal seating area of the engine and install the oil filter by hand turning. Be careful not to twist or damage the seal.
While it doesn't happen very often, make sure the old seal came away with the old filter. If the old seal stays in place, there will be a huge oil spill and it will not seal.
- Tighten the oil filter by the amount indicated in the following table after the seal makes contact with the seating surface (The table states 1 rotation).
IIRC, the Subaru oil filter sticks out sideways from the engine (at least in the ones I've seen), which means there's no logical way to put oil into the filter during the oil change. Just one of those things.
Do not over tighten your filter. The reasons are plentiful, but mainly so the next time you pull the filter off, you can actually get it off without destroying the filter. Secondly, if you over tighten the filter, you can crush the washer and cause it to leak.
- Pour engine oil through the filler neck.
Your choice of oil is correct. I was surprised to find Subaru specifically states "0W-20 synthetic oil is the required oil for optimum engine performance and protection. Convention oil may be used if synthetic oil is unavailable." If the engine is completely drained, use 5.1 quarts of oil to refill.
- Start the engine and make sure that no oil leaks appear around the filter's rubber seal and drain plug.
- Run the engine until it reaches the normal operating temperature. Then turn the ignition switch to the "LOCK" (off) position and wait a few minutes to allow the oil drain back. Check the oil level again and if necessary, add more engine oil.