ANSWER:

You need to follow the link it gives you and create a bundle id. This is a special string that looks like a reversed domain name that is unique for each application you create. For example, if your company is foo.com, you might create a bundle id

com.foo.myApplication

This is done in the Mac (or iOS) dev center under the Identifiers option. Once you’ve done that, you can go back to iTunes Connect and create the application.

gaige from http://stackoverflow.com/questions/16639403