Note that this discount type is only available for Shopify Plus stores as checkout UI extensions are only available for Plus stores.
Only one discount of this type can be created. Due to Shopify limitation, you can only create one discount of this type. When you create a second one, settings of earlier one would be overwritten and you would see weird behavior on your checkout page.
Step 1: Open discounts hub app and click on "Free gift with purchase" discount type.
Step 2: Configure a discount the way you want. Every setting in there should be self explanatory with additional information provided. If anything isn't clear, please contact our support and we are more than happy to clarify.
Step 3: Once discount is setup, you need to add checkout UI component to your checkout. Go to Online Store > Themes > Customize
Step 4: Navigate to checkout page
Step 5: Select "Add app block" from bottom left corner and then select "Free gift with purchase" from Discounts Hub.
Step 6: By default it would add a block below contact section, you can move it anywhere you would like by dragging a block by your mouse.
Step 7: You can add title, description and a button text from right section of your theme editor.
Step 8: Save settings and test your discount.
If your free products are still not visible during checkout, please make sure you have right configured products added in your cart. If still no luck, feel free to contact our support by providing all relevant information.