Yes u can,
1st-Download a program called "Youtube Downloader" from www.youtubedownloader.com
2nd-When u finish downloading the program, open the program and go 2 youtube.com and search for Selena Gomez- Tell me something i dont know
3rd-When u finish searching for the music video that u want it, copy the URL of this video and paste it on youtube downloader program then start downloading.

Here how u can download Selena Gomez-Tell Me Something I Dont Know! I've got that video on my computer!