Choose the "Wonder Trade" option, and trade any desired Pokemon to earn some Poke Miles. You get more Poke Miles based on the distance between you and the person you are trading with. Keep trading the Pokemon you got in Wonder Trade to get more Poke Miles. Use the Poke Miles at the Mileage Club (old man in the white suit) in the Pokemon Center (on South Boulevard) in Lumiose City to purchase Rare Candy (500 Poke Miles) and PP Up (1,000 Poke Miles). Rare Candy allows you to raise a Pokemon to the next level, which is very use when they are at a very high level. The PP Up allows you to add an additional move so you can use more moves in battle.