CSS Head page

Hi all 🙂 

I'm getting some troubles with adding some css code to the main page, I read couple articles that I can't add it without code injection which actually isn't working. 
Everything is fine on the other pages except the head page where all the code is written at the top of the site. 
 

Did I missed something ? I tried with different manners like <style> ... </style> but it also isn't working 😕

Thanks for your answers,
Best regards,

@Twanzz Wrap code in style tag

<style>

paste CSS code here

</style>