You will need to fill in some information on iTunes Connect (https://itunesconnect.apple.com/) for your application. Go to this site and select My Apps.
Click on the plus icon at the top left and click on New App.
Now fill in the relevant information. The Bundle ID list will contain any App ID's that you have created in the Developer Program. This is used to form a link between the App Store and your application.
To begin with fill in whatever information you can in the App Store e.g. product description, pricing etc. Screen shots, video previews and more information can be filled in at a later date.