1.  Go to CATALOG > PRODUCTS and using filters find the product that you want to mark as a product of the day.
   
   
   
   
   
2.  By clicking on the name of the product, or from the action menu, go to edit it.
   
   
3.  From the vertical menu on the left select the tab Special offer and select Product of the day. 
   
   
   
4.  Click Save.

Products tagged in this way, are displayed on the active theme module 'Product of the day'. It must be previously put on the store in Visual style: 

 

CONFIGURATION > LAYOUT > ACTIVE THEME :: From left, click on MODULES :: Click on 'HOMEPAGE' tab, if you wish to show the module on homepage :: take your mouse cursor on the 'AVAILABLE MODULES' and drag and drop the module in the active structure and save it.

You can edit the module and set the format to display the products.