Task: Go to the library section and create a  playlist named  favourite song and add katty perry videos to the playlist 
Steps:
open youtube app
Click on the library section at the bottom right corner of the screen
click on the New playlist icon
select the second and third videos from the recently watched
select the second and third videos from the recently watched
click on the next button at the top right corner of the screen 
click on the title bar 
Enter title as  favourite song
click on the create button