This week is the last week that submissions will be taken for apps that are being entered into the UK Windows 8 app store before the general availability of Windows 8.  So if you want your app to be available on the release date for Windows 8 to the general public then you really need to get your app submitted this week!

There is a fantastic article by Antoine Leblond that runs you through the process of how to submit your Windows 8 App:

http://blogs.msdn.com/b/windowsstore/archive/2012/02/13/submitting-your-windows-8-apps.aspx