You can´t put on the swimsuit in wardrobe at home. Later when you reach corruption 500 you can put on swimsuits at the beach. But going to beach with Ash, Kelly put the swimsuit automaticaly on. You need only to call Ash by phone or enter the beach at a special time, depends on the event. If you mean the first time going to the beach with Ash you can only do this by using your phone.