How do I register my new mini iPad ?

plug it in to a computer and register it through itunes

When you start up your iPad mini for the first time, you will have to answer a lot of questions. One of the very last questions is if you want to register - you reply with yes (this only will appear if you signed up with an Apple ID during the start up process)

If you missed that point you still can register your iPad mini by connecting it to iTunes for the first time. You will be asked to register your device again.