Step 1: Create the benefit

In Marketing -> Benefits, double-click Add New Benefit. Give it a name, then click Add Condition. From the dropdown select Ticket.

Set the conditions you would like the benefit to be applied to. In the example below, a discount of £2 will be applied to tickets for the show Strings Estival Concert. Click OK to save.

Step 2: Create the Discount Scheme
Under Marketing -> Discount Schemes, double-click Add New Discount Scheme. Give it a name, and click Add to add the benefit created in Step 1. You can also restrict the discount to the transaction type, and day that it will be active.

To set a Promo Code for use online, enter it into the edit box as shown below. Be sure to check the "Is Available Online using promo code" checkbox.