To place 'Products' within the 'Featured Products' section, from the store dashboard go to:
> Products > All Products

From within this page click a 'Product' you'd like to place in the 'Featured Products' or hover over a 'Product' with your cursor and click 'Edit':

From within this page scroll down to 'Other' and tick 'Feature this product':

Click 'Publish' at the top of the page:

Once you've finished the above steps for all products you'd like to feature, go to:
> Store Settings > Theme Options > Front Page

Scroll down to the 'Featured' heading and tick the checkbox 'Products':

(*Don't forget to click 'Save Changes' after making alterations*)