Instructions
Travel along Route 209 from HeartHome City to reach Solaceon Town. Head right until you reach a few ledges. Go down the ledges; you will see a house next to the ruins. Enter the house and speak to the person living there to receive the Seal Case, which allows you to purchase and use seals.
Travel along Route 222 on the east side of the map to reach Sunyshore. Enter the store near the middle of the town to purchase some seals. You will find a new set of seals available for sale here each day of the week.
Travel to any Pokemon Center and stand in front of the computer inside of it. Press the "A" button to access the computer, and then select your game character's PC to access it.
Highlight and select the "Ball Capsule" option and then select one of your Poke Balls to place the seal on it.
Drag the seal from the left of the screen to the location on the Poke Ball where you want to place it. You can choose from all the seal designs that you have already bought, but you can only place a maximum of eight seals on each Poke Ball.
Select "Save" when you are done placing the seals on your Poke Balls. You can now assign the Poke Balls to any Pokemon you own; this way, the seals will be visible when you use that particular Pokemon in battle.