1. Add a new customer’s group through the Magento backend area: Customers ->Customer Groups -> Add New Customer Group.
2. Set the discount for the newly created group through the Magento backend area: Promotions -> Catalog Price Rules -> Add New Rule. Using the Customer Groups field you can select the customer groups for which the promotion will be valid. Set the rest of your promo as usual including actions and conditions. Click Save Rule.
3. Once a customer is registered you can change their group through the Magento backend area: Customers -> Manage Customers. Click the Edit link besides the customer and change the group from Account Information -> Customer Group. When you’re ready click on the Save Customer button.
