Once the module is installed, you have the option to Enable or Disable indexing of product custom fields. In order to configure the Custom Fields, you have to create a field with its corresponding values and then associate it to a specific product. Then, you'll be able to manage it on the Doofinder Plugin and index it so it can be visible on your Layer.
If enabled (active), all the fields marked will be indexed. On the example above, we can see some custom fields as “Size” or “Material”.