This feature is not available on the free plan
Cart promotion code field
Discount Ninja includes a promotion code field that can be displayed in the cart (or on any other page). It can be used to apply Discount Ninja promotions as well as Shopify discount codes.
To add the field to your cart liquid, add this line where you want the field to appear:
Enable the field
To enable the field, ensure it is included in your theme (see above) and then go to Settings > Building blocks > Cart promotion code field:
Configure the behavior of the field
You can tweak the behavior of the field in the "Behavior" tab:
if the field should be expanded or collapsed by default
if multiple discount codes can be entered
if Shopify discount codes can be used
what Shopify discount codes can be used (using include and exclude patterns)
Style the field
The settings in the "Button style", "Text box style", "Margin" and "Placement" tabs allow you to configure the color and style of the button and text box. You can also customize or localize the text labels displayed in the "Link, footer & text labels" tab.
To localize the text shown in the promotion code field, check out this article.