I think you need to setup a new account if you want a new address. I don't think it allows you to simply change the address.
You can export your contacts in Hotmail to a file and then import it into your new account. Look at your contacts page, there are some options there.
Also consider your contacts, probably setup your old account to forward mail to your new address, in case people don't know your old one yet, or setup an automated reply to inform them of the change.