How to add a checkout extension
Frequently Bought Together allows adding a checkout extension to show recommendations before proceed to the payment. This feature is available for app Professional plans. However, take into account that due to a current Shopify restriction this kind of extension is allowed only for Shopify Plus stores.
To show recommendations at checkout, go to the theme editor in your Shopify Admin, and select the Checkout and customer accounts view in the top menu:

Then, in the Sections left menu, click on Add block in your desired section (we recommend to use the Order summary section) and select the Frequently Bought Together block:

The block will be added to the section, and you will be able to move it across the section to your desired position. We recommend locate it at the end of the section, under the Total:

Once the block has been added, you can customize some settings in the right menu:

- The title of the block (default Customers also bought:).
- The text of the 'add to cart' button (default Add)
Remember to click on the top right Save button to keep the changes.
Some considerations to take into account:
- all settings related to what recommendations are shown are configured in the app preferences pages.
- if the checkout extension is configured, it will be shown even when the app is disabled in the preferences page.