Where do I find my oneget Windows Package Management installed apps?

It depends on the package provider. If Package Management installs a package from Chocolatey, the install dir is C:\Chocolatey

$ Get-Package openssh | select ProviderName

ProviderName
------------
Chocolatey

And then:

 $ ls C:\Chocolatey\lib\


    Directory: C:\Chocolatey\lib


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----       24/10/2016  11:55 AM                openssh.0.0.1.0

I think I just found the answer. OneGet might have the requirement that script execution is set to remotesigned at least. So, after doing set-executionpolicy remotesigned, oneget finally works!