How do you get an amulet coin in Pokemon pearl?

You go to Hearthome City, and then go to the Amity Square in the northern part of the city with a cute Pokemon. If you don't have one, you can go back to Route 208 to catch a Psyduck, catch a Pachirisu, or go to the south-western part of the city and get a Happiny egg from the hiker, and walk around a lot to make the egg hatch. When you get into Amity Square, go north, into the ruins on the left, take two steps foward, turn to the left, and press a. You will have obtained the Amulet Coin.