Before activating your iPhone 5, make sure you have the latest version of iTunes and that your old phone is backed up to iTunes. You can also back it up to iClouds or your computer. After your old phone is backed up shut is down and follow these steps:

  • Plug your iPhone 5 into your computer or choose to activate it via Wi-Fi.
  • Turn on your iPhone 5 by pressing the on/off button. This is located at the top right of your iPhone, you can then follow the Setup Assistant to sign in.

This will complete the process along with giving you the information you need in order to restore the backup from your old iPhone into your iPhone 5.

Resource: WikiHow