Nevigate to the youtube video which you want to cut. Click the video link as you do to watch on youtube website.

Now, under video title you will see ytcutter interface. Drag and start/end markers and click Select this part button to add selected part into a list.

Select all the parts you need to cut from yt video, then select output format mp3/mp4, and whether you want to merge all the parts or not. Then click Start Cutting button.

This will queue the downloads into the list, wait for them to finish download and then you can watch them.