Open the Settings application.
Tap Security.
Tap Encrypt device or Enable storage encryption.
In order to encrypt the device, the battery status needs to be over 80% and the charger plugged in and supplying power.
Access the Encryption settings, then tap Encrypt device.
Tap the Encrypt device button at the bottom of the screen.
Enter your current encryption PIN or set the numeric PIN if it has not been previously set.
Please be aware that device encryption may take more than an hour, and the phone may restart several times.
Access the Encryption settings, then tap Enable storage encryption.
Read the general description.
Tap the Enable ecryption button at the bottom of the screen. Protect the information in your phone's storage by entering a PIN.
You can disable the storage encryption feature, if you no longer want to encrypt the files saved in your storage. However, previously encrypted files will remain as encrypted.
Open the Settings application, then tap Security.
Tap Enable storage encryption.
Enter your current PIN.
Tap the Disable encryption button at the bottom of the screen.