Child theme allows you to modify the theme without actually modifying the theme’s core codes, so it makes sure that you can safely update the theme whenever there’s a new update without losing your modifications.
I strongly recommend that you use child theme to modify the theme instead of modifying the theme’s files directly.
It’s quite easy to do. Here’s how:
Create a graphene-child folder in wp-content/themes/
Create a new style.css file inside the graphene-child folder
Copy and paste the following code into the new style.css
Theme Name: Graphene Child
Theme URI: http://www.yoursite.com/
Description: Child theme for the Graphene theme
Author: Your name here
Author URI: http://www.yoursite.com/author/
/* Your modification goes under this line */
You will only need to modify the values of the properties for the elements that you want to modify. There’s no need to copy and paste the entire style.css.
Go to your WordPress Appearance > Themes admin page and activate the child theme.
Use You favorite CSS editor making Your new Child Theme files eg.: style.css & functions.php or get this free CSS editor: Komodo Edit.
Use Your favorite FTP software making wp-content/themes/graphene-child catalog on Web server & upload of Your new Child Theme files eg.: style.css & functions.php or get this free FTP software: FileZilla.