Locating a Device Identifier
Locate a device’s identifier which you'll use to register the device for development with Member Center.
For iOS apps, connect your device to your Mac.
In the Devices window under Devices, select your device.
The device identifier appears in the Identifier field.
If you are registering multiple devices for development with Member Center, you need to locate the device IDs for each device or use iPhone Configuration Utility to create a devices file that you upload to Member Center, as described in Registering Multiple Devices.