I have not done it but there is typically an adjustment screw somewhere embedded in the light housing in the engine bay. I'll bet if you run up to your local dealer and just ask a tech, he'll show it to you for free.

 

Turn blue adjuster on the back of the headlight assembly with a 6mm allen key clockwise. ½ a turn should make a noticeable difference, oncoming drivers will let you know if you have gone too far :surprise:.

 

Thank you so much! As soon as we get above zero degrees Im doing this. I appreciate your time and knowlege.

 

My MY18 Impreza low beam aim can be manually adjusted from inside the cab. There are small servomotors that aim the headlight. However, the highest setting is not aimed high enough. To adjust the low beam aim, look for a 3/4 inch white plastic gear wheel on the back of the headlight cluster, accessed from the engine bay. The gear wheel has an 8mm moulded plastic nut. Rotate the plastic nut with an 8mm wrench. With each quarter turn you'll see a height difference.
If you have your car serviced at a dealer, they'll want to reset the headlight aim. Tell them not to.