I am trying to evolve my Eevee into Sylveon in Pokemon Moon, but I can't seem to. Do I feed it a rare candy when it has a lot of friendship or do I have to do something different?
To start things off, get Eevee to learn a Fairy type move. Next, head to Pokémon Refresh via the menu and earn two hearts by feeding it Poké Beans and petting it.
When everything's all set up, it'll evolve into Sylveon when it levels up.
Source: http://www.techtimes.com/articles/187026/20161125/pokémon-sun-and-moon-guide-how-to-evolve-eevee-into-sylveon-leafeon-glaceon-and-more.htm