How to lock my s6 edge on youtube and disable all touchscreen capablilty

[AC Question]

Does anyone know how to lock your screen on a galaxy s6 edge I want to go for a run while listening to music on youtube but it always changes songs and what not while bouncing around I have accidently done this before so I know you can do it there Is a little lock symbol that pops up on the screen and you can't do anything the only way out is to hold the power button and the home button can someone please tell me how to access this lock