1. Open System Preferences.
2. Click the Security & Privacy preference pane.
3. Click the lock icon in the bottom-left corner of the window.
4. Enter an administrator user name and password.
5. Click "Turn Off FileVault..."
6. Click "Restart & Turn Off Encryption"
7. Revisit Security & Privacy preference pane in System Preferences to check decryption status.
8. When decryption is complete, System Preferences will report "FileVault is turned off".