To transfer resources between islands, you should build the Zeppelin Harbour. This building gives you a zeppelin using which you can send resources you want to another island. As soon as your construction will be completed, tap the Map icon in the lower part of the screen and go to the map. There you will see an icon with the zeppelin: tap it to choose resources you want to send and its destination point. Please, note that one zeppelin can carry only one type of resources. The amount of your zeppelins depends on the level of your Zeppelin Harbour.