Getting a new iPhone up and running is a simple process -- you simply switch it on and select the "Set Up as a New iPhone" option. If you want to use your iPhone as a replacement for an old model, however, you can restore information from a backup you have made on your computer or online. This will mean that your replacement iPhone will have the same content and settings as your old one.
If you still have your old iPhone, sync it to your computer and select the "Back Up" option to make sure your backup is completely up to date before setting up the new handset. If you don't have your old iPhone, you will have to use the information from the last backup you've made. You may be able to manually re-download and reinstall any apps or other content you've bought from the iTunes store since that backup.
To restore a backup from your computer, do not select "Set Up as New iPhone" on your new handset; instead select "Restore from iTunes Backup." You'll then be asked to connect the phone to your computer. When prompted by the computer to choose between setting your device up as a new iPhone and restoring from a backup, choose the "Restore" option. If you've previously synced multiple Apple devices to the computer, use the drop-down menu to select your previous iPhone before clicking "Continue." ITunes then automatically restores from the backup and restarts your iPhone, ready to use.
If both your old and replacement iPhones ran iOS 5 or later and you had an iCloud account, you can restore information from your iCloud backup. To do this, simply choose "Restore from iCloud Backup" on your replacement handset during setup. If you have multiple Apple devices, make sure you select the correct iCloud backup and not, for example, a backup of your iPad. Your phone will use an Internet connection while restoring from iCloud, so use Wi-Fi to avoid data charges.
Apple's technical setup means that you cannot restore information from an old iPhone onto a new iPhone if the new iPhone runs an older edition of iOS. This could be an issue if your replacement iPhone is an older model or a used handset. If you are in this situation, you will need to use the "Set Up as a New iPhone" option, then update its operating system to the latest edition of iOS before restoring a backup from your old iPhone.