Get off on Harbor Blvd, and turn right, then get immediately in your left lane and turn left on Ball. Stay in your left lane and turn left on Disneyland Drive - it will be on your left to check in. Then you'll get a parking permit to park in the lot.
You can also get off on Harbor & turn left, get in your right lane, turn right on Katella & stay in the right lane, turning right on Disneyland Drive - it will be on your right side.