Bulk Discounts is a very simple app and most of the usual functions for editing discount codes can be found in Shopify's Discount screen in their admin. We decided there is no reason to change this so you can view, edit, and delete codes, individually or in bulk, in Shopify's Admin.
1. Click Discounts on the left of the Shopify Admin
2. Select your discount set - Any sets created through an app will say so next to the name
3. Click View all codes
In there, you can do anything you want with the codes.