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".