Okay, I want to build an App that allows me to create questions on StackExchange. I registered it here on Stackapps but now when I want to create a question I get this message:

Applications must have a registered Stack Apps post to write

On my profile the Stack Apps Post is set to Not set and it tells me that my app has to be published first:

Stack Apps Post

Not Set

When you've published your application, it should be listed on Stack Apps with the app or script tags.

But how should I publish something, that I could not initially test? And how would I publish my App (not that I would be ready for this now).