I am installing my own app in iTunes, and found it to be unknown genre. Since my app is an News based Genre, i need to make is shown as a news genre instead of unknown Genre
You don't get to set the genre until you submit the application to the App Store. In the process for submitting an application to the App Store you get to set the Primary and Secondary categories, just like slf said. Before submission, you're app has no genre.
I'm not sure I'm clear on what you are asking, but when you submit your application to the App Store you will be prompted for the Primary and Secondary category for your application. Users will see that.
If your app is Ad Hoc distributed or Enterprise distributed, this does not let you set the application category and it stays as "Unknown Genre".
We still don't have an answer to that condition.