This option is located in the Theme Options > Custom CSS tab.

Sonnet allows you to add additional CSS code directly from the editor. Custom CSS option allows adding custom CSS to the whole website which means it will load on every page of your WordPress website and may affect styling.

Please enter the code in the editor. (Fig. 1)

Custom CSS option Screenshot.
Fig. 1. Custom CSS option Screenshot.

 

Custom CSS Code – Illustrated as A.  Please enter the code in the editor.