Please follow the below steps to transfer the game from one device to another.
iOS-iOS (iPhone, iPad, iPod Touch)
Make sure that the village you want to transfer is already linked to your Game Center account. Then, sign into the same Game Center on the device you’d like to transfer to. After launching Clash of Clans, you should be prompted to load your desired village.
Connect the village you’d like to transfer to Google+ Sign-in. Then add the same Google+ account to the Settings on the new device (Users > Add new). Then, launch Clash of Clans, tap on “Sign in to Google+” and select your email address. You’ll see a popup confirming the transfer.
iOS-Android or vice versa
Make sure you’ve installed the game on both devices, keeping them both on-hand. Use the ‘Link a device’ feature in the in-game settings, then press ‘Link a device’ on both. Follow the on-screen instructions to complete the transfer.
This feature cannot be reused. Following use of the ‘Link a device’ feature, your game will be connected to both Game Center and Google+. In the future, you’ll be able to use those services to connect your village to further devices. This is why you only can only use ‘Link a device’ once.