Your title says "Turn off" (disable) but the message says "Enable". So I am including both.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.
To get out of Safe Mode, please try the following.
1. Touch and Hold the "Power" key.
2. Tap "Power Off".
3. Once the phone is off, Touch and Hold the "Power" key again to restart.
The phone should now be out of...