Well the Meta data is all the data including (1) your application’s name, (2) the version number, (3) the primary (and an optional secondary) category, (4) a concise description, (5) keywords, and (6) a support URL etc which you should know for uploading an app to the Apple Store. You will have to use this information while uploading.
Supplying information to the App store can be done once you have collected all the data.
I think you should go through this tutorial on how to submit an App to the Apple store.
EDIT :
The Metadata has nothing to do with the xcode project or the .plist file whatsoever. You DONT have to do anything with it. This information you have to enter in the website of the Apple store when they ask for it .