It's easy find Echoes+ when you know a little more about where Steam stores your applications files. The quickest way is to open up Steam, click on your Library and make sure you're in the software section where you'll find AGK2.

When you see the application's name, right click on it and you should see a pop up menu like this;


Click on the Properties option which will then present this screen;


Now click on the LOCAL FILES tab and then on Browse Local Files... button. A file selector will appear like this showing you where AGK2 is on your hard drive;


Open the folder labelled "Tier2" and then inside that the folder labelled Showcase;


This is where Echoes+ is, now just run the application and have some fun!