In order to sign up to Xbox Live Indie Games portal you simply need to go to http://create.msdn.com
However first you need to first create an Xbox Live account. – If you previously had an App Hub Account, there is no path for you to register on Xbox Indie Games Portal for free as a student, so you need to create a brand new account, i.e. a new Microsoft Account (previously Windows Live ID). – It is important that you follow the steps below exactly in the order described.