The Featured Products block on homepage is a widget to manage the feature products.
Please login into your Magento admin then select "CONTENTS"->"Blocks"
On Block Listing Page choose block name "Homepage Featured Products" and click on edit.
On edit page you will see widget icon. When clicked, it will popup your widget options to allow you to change filters.
Condition of widget is currently getting 12 products from category with id 1023 ( VITAMINS & SUPPLEMENTS->Immune Support->Cold & Flu ).
On widget conditions we can change condition to widget filter products by attribute or category or brand or SKUs. For an easy setup create a category with name such as "Featured Product" and add a product they want to make as a featured product to change conditions.