Go to Your Settings App
Go to Touch ID & Passcode
Enter Your Passcode (if you have one)
Go Into Touch ID
You'll See this Screen
Now Place Your Finger on Your Home Button, Like You're Getting Into Your Phone. Whatever Finger You Have Down, it Will Darken the Bar That Corresponds. This Means its Learning Your Finger Better.
Mine Was My Right Thumb, and You Can See The 'Right Thumb' Bar Got Darker.
Any Questions Feel Free to Ask. Thanks!!
- IPhone 5S