Update iOS software for iPhone 5 wirelessly by selecting Install Now on the pop-up software update notification screen. Then, tap Download and Install from the Software Update Screen. Select Install or Later. If choosing to download the software later, select either Install Tonight or Remind Me Later.
If the automatic pop-up software update notification does not appear on the iPhone, tap Settings, then select General and then choose Software Update to enter the update mode manually.
To update the iOS software without a connection to a Wi-Fi network, update the software by connecting the phone to iTunes. First, ensure that the latest iTunes version is installed on the computer. Then, open iTunes, and connect the iPhone. Select the iPhone by clicking the iPhone icon in the upper left hand corner of the window. Click Summary under Settings, and then click Check for Update. Next, click Download and Update.
Before installing an update, back up the data on the phone to iCloud or iTunes. To update using iCloud, connect the iPhone to a Wi-Fi network, tap Settings, then iCloud and then Backup. Turn on the iCloud Backup from this screen, and then select Back Up Now. To update using iTunes, open iTunes, and connect the iPhone to the computer. Next, click File, then select Devices and then press Transfer Purchases. Finally, from the Summary screen, click Back Up Now under the Backups section.