How to edit your style.css on another code editor.

Did you upload your modified style.css?

Were do I upload it.

Clear your browser cache, or make sure you’re using the right selectors.

You need to upload your new style.css via FTP to your web host. If you have no idea what FTP is, read here.

Otherwise, falling back to the built-in editor of WordPress is probably a better choice.

Also, you should avoid editing the parent theme’s CSS if possible. Use JetPack’s new custom CSS feature or create a child theme to add your customization. See WordPress child-theme documentation for more info.