Hi there!
Thanks for your query.
Please check this out:
https://www.joomshaper.com/documentation/joomla-templates/educon/feature-box-customization
Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.
Path towards custom CSS(Joomla 4): System>Site Templates Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.
https://prnt.sc/5mBuSRh907N3
https://prnt.sc/ooiq-lkMEXr_
https://prnt.sc/nunlX-f5AhK1
Have a nice day!
Best Regards