Sidechain input - help with setup

I'm new to audition.  I want to use the matcheq feature in this plugin.  My reference is in track 2 and the source to change in track 1.  I get from various yt videos that I probably need to set the side chain for track 1 to track 2... 

I believe I need to set the sidechain to track 2.  I looked and dont see documentation on this simple step.  I believe I hit the sends button and then slick S1:None -> Side Chain -- but the option is grayed out...?

Help!