Custom CSS

Hi,

I follow the step in here for use custom.css

How can I add custom theme?
– Now, you can add your custom stylesheet in your’s theme directory.
– If you don’t have “css” folder in your WordPress theme, you must create it.
– Then, in this folder create another – named “wp-posts-carousel” and now you can move custom stylesheets in there 🙂

Is there any next configuration? Seems after I create the css file, it didn’t give affect at front end

Please advice

Thanks

https://ww.wp.xz.cn/plugins/wp-posts-carousel/