Ok,
I've spent a few hours trying to find an answer to this question and had no luck what so ever.
I am creating an appium automated test using xcode Version 9.3.1 I need to locate the .app file so I can add it to my desired capabilities and I cant find it in any folder.
Breaking it this down in the most basic fashion, how do I locate the .app file so I can add it to my ios appium automated testing?
Out of curiousity would I need to use something like homebrew to locate it?
Or can I find from a specific menu in xcode?

By default Xcode stores the derived data for all projects in a single shared folder under your home directory at the following location:
From Xcode 6, you can access or change derived data location from Preferences -> Locations Tab
but you can setup in xcode:
locate "Derived data:"
here is how to setup https://www.youtube.com/watch?v=MVVRsR9XenQ