Go to General settings> Click on custom css/js code and after that you will enter to this page as mentioned in the screenshot below :

Custom CSS/JS Code #
Add custom CSS or JavaScript/jQuery to enhance your store’s functionality or track specific actions like conversions.
Use this section to insert custom code that runs based on predefined triggers or page events.
Custom CSS #
Style your store components as needed using custom CSS.
⚠️ Important: Use
!importantwith every CSS property to ensure your styles are applied correctly.
Custom JavaScript / jQuery #
Inject custom JavaScript or jQuery to add dynamic behavior or run tracking scripts.
⚠️ Note: Always use double quotes (
") around attribute values.