Voting starts on April 16th and will end on May 8th. Participants can cast their votes at polling boxes found at Pokémon Centers and Toys 'R' Us locations in Japan, online, using a digital TV remote during the Pokémon XY & Z broadcast on TV Tokyo, and using a ballot in Coro Coro Comic.
The intermediate results will be announced on April 28th, which will be followed by the final results on the Oha Suta TV show on June 7th. A celebration will follow at a theater in Tokyo at a later date.
[Source: Anime News Network]