When building your website with WordPress, you will install different plugins to cover all of the functionalities you need.
WordPress is perfect for that since it has more than 60 000 plugins available from its repository. Now it comes at a cost, somehow you’re going to need to find ways for each plugin you install on your site to play along well with each other.
Often you’re going to need to write some custom CSS rules, so that your theme appears exactly the way you want.
In order to do that you can use WordPress’ Customizer.
When you are connected to the backend of your WordPress’ site:
- click Appearance > Customize
- Then click Additional CSS
- Then enter the CSS rule you’ve carefully crafted
- And hit Publish
That was easy wasn’t it?
Go to Customizer 
The customizer show 
Customizer additional css panel 
New css rules are applied
