1. Catch a Nincada 2. Make sure you have an empty spot in your party and an extra Pokeball in your bag. 3. Level up Nincada to Lvl. 20. Let it evolve into Ninjask. 4. You will have a Lvl. 20 Shedinja in the previously empty space in your party. It will have the same moveset as your Ninjask does now, but will learn a completely different set of moves as it levels up.