I tried installing animation nodes. Blender thought it installed it but it actually didn't (because it was the windows version and I was using Linux). I realized this when I ran into this problem. So I deleted that zip and downloaded the linux one. Now it shows up in the Add-ons folder when I select the .zip (as shown below)
Thinking that Animation Nodes is already installed, even though the Windows version didn't show up in the Add-ons panel or anywhere on my hard drive. How can I get the proper version installed?