Ok to start all fresh and new, you need to make a new account totally from Gamigo with the email and everything. To do that You go to the Savage Hunt Official website and click on "register for free". Your old Infernum login information is no good anymore unless you migrate, so make a new account like you never played before.
Then you also need to download the new client. Any client you had played before is no good anymore. There are 2 different clients available. One for Dragon's Prophet and One for Savage Hunt. Your fresh new account login and password will work in both and they are different games.
The downloads can be found in this Thread: