Pardom my ignorance, where should I put this code?
Please put it to Appearance > Customize > Additional CSS
No, I was refer to WP Categories element from Visual Composer. Please see screenshot: https://cl.ly/1W0V0k2i2F3S
Actually, you don’t have to add it manually because I already gave you the page contents. But, it seems you not activate the Visual Composer plugin yet?