Using the "loop" function

Anything that doesn't fit into other topics goes here!
There must be something that I'm not getting about those two green arrow things that you move around to play and loop a specific piece of my music, because I don't know how to do it. I've only gotten as far as pressing the button that makes the arrows turn bright green. And I've looked for tutorials too, but none of them show me how to do it.
use the right mouse click to either drag or move the "end" loop point and both left and right click and drag or move to the "start" loop point, <<< this is the equivalent of middle mouse click on a mouse;)
Ok thanks!