To prepare your iPhone 5 for the battery replacement process, please follow the steps below:
Back up your data to iTunes or iCloud
Turn off Find my iPhone
Erase data and settings in Settings > General > Reset > Erase all Content and Settings
Note: If your iPhone 5 has any damage such as a cracked screen which impairs the replacement of the battery, that issue will need to be resolved prior to the battery replacement. In some cases, there may be a cost associated with the repair.