Step-by-Step:

(1)Generally, you just copy the video's link from youtube.com, example: http://www.youtube.com/watch?v=M-dmO1hTBAI

(2)Run HiDownload Platinum

(3)click "Add" button, and open the add window.

(4)you can find the video's link in URL editbox

(5)click <OK> button, HiDownload Platinum start to download the video.

Note:

If some youtube's videos can not be downloaded, then you need to startup sniffer and capture the video's link, then download it. more details, please read: Just one-click, download stream video