Hi
You have a guide to make a project from scracth here Blueprint Empty Project Sample — AudioAnalyzer 2.09 documentation
If you want only to use the loopback source you can skip the content related to the media folder of the guide.
This image resume how to use the plugin:
Just replace this nodes for loopback:
“Init Player Audio” by **“Init Loopback Audio” **
“Play” by **“Start Loopback” **
“Is Playing” by **“Is Loopback capturing” **
Also you have a project using loopback source here too: parallelcube.com/audioanalyzer-projects/#pr06
https://youtube.com/watch?v=wvRJUXPsj7c
In that page you have too more projects like the guide project.
Try it and if you have more questions contact again 