You can set s.products in the 'Customize Page Code' editor within the tool settings, or in the editor in the Adobe Analytics section of a rule. The syntax is written as follows:
s.events="ProdView"
s.products="Category;Product"
To incorporate data elements, the following syntax logic can be used:
s.events="ProdView"
s.products = _satellite.getVar("myCategory") + ";" + _satellite.getVar("myProduct")
For more examples, check out Jenn Kunz's guide here: https://www.digitaldatatactics.com/index.php/dtm-reference-tools/
For more information on the product string, reference the s.products documentation here: https://marketing.adobe.com/resources/help/en_US/sc/implement/products.html