I'm not sure I fully understand the question here .... I'm assuming you currently have a Galaxy S3 and your dad is giving you an I phone 5, which is unlocked and you want to start using the I phone ??
The I phone is unlocked, so you can simply take the sim card out of your old phone and transfer it to the new one. If they are different sizes, you can buy sim card adapters.
If you want to transfer any pictures, videos, etc .. I suppose the easiest way would be to Bluetooth them, depending on how many you've got ??