Luckii

(You can't switch your Pumpkaboo if your team doesn't have all six Pokemon slots used, and you need one Boxed Pokemon.) Step 1.) Press 'Your Account'. Step 2.) Press 'Your Pokemon Team'. Step 3.) Press 'Change Team'. Step 4.) You'll see a 'Search:' button on your screen, you search a Pokemon that's inside your box, then, you click your Pumpkaboo and that Pokemon, you'll find that both of their screen-things are red. Step 5.) You press '<Switch>'. Hope it helped, but it might not be the same for your device, since I'm on a laptop.