Instructions
Leave Littleroot Town, the town where you start the game, via the northern exit. Walk north on Route 101 until you reach Oldale Town.
Walk west from Oldale Town on Route 102. Route 102 leads you to Petalburg City.
Walk west on the path when you reach Petalburg City. At the end of the path, go north. When you reach the Pokemon Gym, walk west.
Go north at the junction. Follow the path to enter Wally's house. If you already defeated Norman in the Petalburg Gym, talk to Wally's parents to receive HM03, Surf.