Well do as usual by testing your app in the simulator or on your iDevice through Xcode/organizer.
Then, when you are (or feel) ready, goto the iTunes Connect portal. Of course you have to be a registered Apple iOS developer.
Juste read the docs from iTunes Connect (less than 300 pages

...
In short :
- add some specific files (through Copy files in LC) to your app bundle - icons for iTunes and App Store namely
- create your standalone
- zip it
- Use iTunes Connect to create a new app, and upload other files to it (like the iTunes artwork file)
- Then upload your zipped binary
- Cross your fingers and it is done
So some files have to be included before you create your standalone in LC, and others have to be included only at the last moment through the official Apple iTunes Connect portal.