Checkout upsells - Add-ons
Add-ons are displayed when the customer navigates to the checkout page. An add-on product will be displayed within a dialog to encourage customers to purchase additional products before checkout.
To create an add-on rule go to Online store > Online setup > Product upsell. Tap 
Add-on to create an add-on rule. Complete the following information:
Title - Add a title you wish to display on the add-on dialog to promote the product.
Priority - If multiple rules match the product that is added to the basket the rule with the highest priority will be displayed (0 then 1 being the highest priority, 10 being a lower priority)
Publish this item - Checking this option means the rule is active
Create the rule - Define when the product add-on should be displayed. If the product added to the basket matches the category, brand and tag defined then display the selected product
Tap 
Save to save the add-on rule. All add-on rules are displayed in a list in the Add-on section sortable by all columns. Tap the product name from the add-on list to view the rule. All fields can be updated and the rule can be unpublished if you no longer wish to use it but don't wish to delete it. Tap
Save to save any amendments or 
Delete to delete the rule.
Related products
Related products are displayed in a product carousel beneath the product on an individual product page. A maximum of 12 products will be displayed.
By default, the first 12 products within the same category will be displayed. If the product is part of a composite, the remaining products within that composite plus any colour variants will be displayed first as part of the 12 products. When creating a related products rule, the products within the composite take priority, then the matching rule products will be displayed. Create a title for the section such as You may also like then create the related product rules.
To create a related product rule go to Online store > Online setup > Product upsell. Tap 
Related product to create a related product rule. Complete the following information:
Priority - If multiple rules match the product display up to 12 products in priority order. The rule with the highest priority will be displayed (0 then 1 being the highest priority, 10 being a lower priority)
Publish this item - Checking this option means the rule is active
Viewing product - Define what types of products the customer needs to view to display products matching the Related products rule below. Set the rule parameters; select the category, brand and tag. Related products are shown if the customer views a product with a matching Viewing product rule
Related products - Define what types of products should be displayed if the customer is viewing a product that matches the Viewing product rule above. Set the rule parameters; select the category, brand and tag. Products with matching rule parameters will be displayed in the related products section (Up to 12)
Tap Save to save the related products rule. All related product rules are displayed in a list in the Related products section sortable by all columns. Tap the product name from the related products list to view the rule.
All fields can be updated and the rule can be unpublished if you no longer wish to use it but don't wish to delete it. Tap Save to save any amendments or 
Delete to delete the rule.