Where is my application binary in Xcode to submit?

Look at a path something like this:

"/Users/{user}/Library/Developer/Xcode/DerivedData/{appname-somehash}/Build/Products/Debug-iphoneos/{app-name}.app"

You can run "find" to locate it.

You could use XCode and on the left expand "Products". Highlight your .app and then go up top where it says "Action" drop that down and select "Reveal in Finder"

By default, you'll see a build directory inside the directory containing your project.
In that build directory:

<Project Name>.build` contains all the object files created during compilation

and a series of folders with the following naming scheme:

<build setting>-<platform>

You're likely looking for something like "Release-iphoneos". In that folder you should find the .app package to submit.