How to add CSS-code to my Sharepoint List?

I have created a Sharepoint List. I need to change the font of the list in CSS-code

<style type="text/css">
   .ms-rtestate-write 
   {
       FONT-FAMILY: Calibri; 
       COLOR: grey; 
       FONT-SIZE: 11pt
   }
</style>

But how can i add the css-code to my list. My List is not on a page
so i can not use a webpart.

Greetings,

Peter