Q: Iphone 6s : applecare

E' possibile "acquistare/aggiungere" la garanzia Apple care per un dispositivo (Iphone 6S) acquistato in un centro diverso da applestore?

Can I add an apple care buying it from an apple store (or online) if I've bought my iphone 6s in another store? (different from an apple store)? Or shall I buy the iphone from an apple store in order to have the possibility to add the apple care on my device?

Thank you