Both iPhones must be connected to a Wi-Fi network. To connect, tap Wi-Fi near the top of the Settings menu, slide Wi-Fi to the “On” (green) position, and tap a network from the list under “Choose a network. . . " Enter a password if prompted to do so.
If you are not signed in, tap Sign in to (Your Device), enter your Apple ID and password, then tap Sign In. If you are running an older version of iOS, you may not need to do this step.
If it’s not already green, slide “iCloud Backup” to the “On” position.
If you are not signed in, tap Sign in to (Your Device), enter your Apple ID and password, then tap Sign In. If you are running an older version of iOS, you may not need to do this step.