1. Insert USB hard drive to DVR's USB port.
2. Go to play back in system.
3. Click play to play back video first.
4. drag the bar to time where you want to cut off and click scissor to begin cutting.
5. drag the bar to time where you want to end and click scissor again to stop editing.
6. Click back up next to scissor icon.
7. click backup and select the file you cut off just now to back up