Find Playlist that you want to download and copy it's URL. For example : https://www.YouTube.com /playlist?list=PL41lfR-6DnOphKZdzukiMDU5B6i_JLY8w
Now just Select "Playlist Download" from tab bar.
Paste YouTube Playlist URL in appropriate text-box and click on "Download" button.
Wait until all video get processed and then click on "Download .txt File" button.
Go to Task->Import->From text file and import downloaded .txt file and check videos that you want to download and just click on "OK" button.