In the store administration select Marketing ...> Promotions and select the “Add Promotion”. The screen provides fields for you to input a promotion name and promotion properties. Input the properties of this promotion including the start and end dates, whether this promotion is for free or discounted items and which items are included then choose the Customer Group to which this promotion applies.
Customer Access to Special Prices
For the promotion and customer group features to function effectively the customers must have accounts and they must be logged in when they visit the site. When a customer creates an account in your store, the store asks the customer if they should remember the customer for their next visit. This technique allows your store software to recognize that customer when they visit again. The advantage of this technique is that a customer with an account is automatically recognized when they visit. Note: customers will not see the special pricing until checkout time.
If you create the account for the customer then the customer is not recognized until the first time that they login. If for any reason a customer deletes the cookie file from their computer or visits your store from another computer the store will not recognize them automatically.
NOTE: Even though a customer can create their own account they cannot assign themselves to any of your existing groups. Customers that have access to special groups, discounts or pricing on products may not even know that they are part of a special group. If you want to draw attention to the special treatment you will have to use other marketing means to communicate your message.