I need the CSS file location for Elemental Theme
Thanks for helping.
The CSS file path for the default Elemental theme is this:
Editing this file directly requires an understanding of Less (http://lesscss.org/features/ ) and knowing that any changes made to it will be overridden when you update concrete5.
To prevent the CSS files from being overridden, you will need to make a copy of the theme.
A simpler alternative to all of this is to add CSS to the Customize CSS section instead.
Toolbar > Page Settings (gear icon) > Design > Theme > Customize > Custom CSS gear icon button