How to open a node on unreal and see what is inside it

i am new to unreal engine. The below is the blue print of a button (i am not the one who created).i want to open the "Call Button Clicked" and change the things when the button click happens. But i don't know how to do this. When the mouse hover over it, its showing a name "k2node call delegate". i want to know what happens when "call button clicked" is called. I am using Unreal 4.27.2 .

it's calling delegate and when it's called all who bind to this will receive notification.

you could find bindings by right-click on this delegate and find reference, there you could find appropriate binding from other classes.