You will get the Contest Pass from Lisia in Slateport City. To obtain it, you need to first deliver the Devon Parts to Captain Stern. The Contest Pass is part of the main story, so it’s an unmissable key item.
The Contest Costume becomes available as soon as you get the Contest Pass, and it’s an optional key item. You can obtain the Contest Costume in any Contest Hall when you try to enter a Contest Spectacular for the first time.
These two items are both necessary if you want to sign up for Contests around Hoenn.
Getting the Contest Pass (Step-by-Step)
After delivering the Devon Parts to Captain Stern in the Oceanic Museum, stay in Slateport City. We’ll guide you on exactly where to go to get your Contest Pass.
Step 1: From the Ocean Museum, go to the main street and head north.
Step 2: Keep heading north past the Pokémon Center and the Poké Mart, going towards the exit to Route 110.
Step 3: A short cutscene will play just before you reach the exit to Route 110. Everything will proceed automatically from this point.
Step 4: Following a brief dialogue, Lisia will give you the Contest Pass and the Pokéblock Kit.
After obtaining the Contest Pass and the Pokéblock Kit, you can advance the main story and continue to Route 110.
Getting the Contest Costume (Step-by-Step)
As soon as the previous cutscene ends, you will find yourself outside the Contest Hall.
Enter the building.
Note: You can also obtain the Contest Costume in any of the other three Contest Halls. They are located in Verdanturf Town, Fallarbor Town, and Lilycove City.
The step-by-step process below is for Slateport, but it will be the exact same steps in all locations.
Step 1: Inside the Contest Hall, head to the counter.
Step 2: Lisia will stop you just before you reach the counter, triggering another cutscene.
Everything proceeds automatically from this point on.
Step 3: After another short dialogue, she will give you the Contest Costume.
Once you have the two items, you will be able to enter a Contest Spectacular for the first time.