01) Access the Control Panel
02) After login click on Configuration >> Product Listing >> select the options below and click on EDIT
Enable / Disable Custom Source Code After Buttom Buy in Product Page: true = enable / false = disable
Turns on this feature to appear on all product pages below the buy button, does not appear on the list, only when you access the product page
Custom Source Code After Buttom Buy in Product Page:
In this field you can enter an html code, text or image
After clicking on the UPDATE button