New customizer feature with WordPress 4.7 and upward
Adding CSS without editing any theme CSS files
To change, add or tryout your custom CSS is a often called question in many support threads. The answers are at most only the CSS snippet you may add to solve your problem but not how to add because this part is very inconveenient. You can try it with the browser tools and if it works use your FTP client or the editor behind appearance. With WordPress 4.7 there is a elegant and quite easy way to add small inline CSS. Users can add custom CSS directly from WordPress admin area. This is super-easy and you would be able to see your changes with a live preview instantly.
There are many ways in the WordPress admin back-end go to the customizer.
WordPress provides with the customizer, a “live-preview” editor. You will see options which was implemented by you Theme. All options are change immediately while editing. That’s why it called the “Live-Preview” editor.
Changes will be available after applied
The customizer is opened with the left side panel and shows a bunch of options. One of this option panels is the tab “Additional CSS”. Click this tab.
The tab opens and show a large text box where you can add custom CSS selectors. And the customizer isn’t the customizer wouldn’t be added or changed CSS rules immediately shown while writhing at your site in the right side.
After you’re satisfied with your added CSS rules don’t forget to click on the “Save & Publish” button on the top of the left side.
This easy and fast method can’t solve all. So called “inline code” for CSS is also for smaller snippets good. As opposed to external added files, which was added once and cached by the browser, are made for large CSS code because the code’s logic is separated and better to update and maintain.
Now, the new added CSS selectors looks create within the head-area on the lowest position to override the other CSS.