First introduced in Pokemon Ruby and Sapphire, Pokemon Contests make a return to the franchise' latest installment, now with better features. As part of your adventure, you'll eventually come across Lisia, the popular Contest Idol in the region. She'll provide helpful tips about these activities, and provide your character with a costume. After completing your first contest, she'll also provide you with a Cosplay Pikachu.
The contest has five kinds. Your Pokémon will be judged on its appeal based on one of those five conditions. Choose a contest condition in which your Pokémon excels, and enter it in one of the corresponding contests!
Each kind of contest is also split into four ranks. You'll start at the bottom which is Normal Rank. After winning the current rank, you can go up to Super, Hyper, and Master Rank.