When you setup your iPhone for the first time, you are asked to select your iPhone's language. But after that you need to do as follows to change language on iPhone 5 running iOS 9.x:
1. Open the Settings and go to the General settings.
2. Scroll all the way down to the Language & Region settings
3. Tap the iPhone Language option and change the language on iPhone 5.
Tip: If you have accidentally changed the language on your iPhone, the Language & Region is the 5th item in the General menu from the bottom, and the iPhone Language is the first item in its menu.