Capture the Jellies and take them back to Jelly-nate, their own planet. You'll have to buy food, place it on your beach and wait for them to come. Once they appear, you will be able to capture them through a mini-game. The Jellies that you can encounter change according to the place and the food. Most of them can grow after you capture a certain amount of the same species. The game will get more difficult as you progress, but don't worry, you'll be able to acquire items for your character and the beach to help you and evolve your jellies!