How to insert CSS into html?

Question

Although I have go into class CSS, but still didn't get how to insert CSS into html.
Did I possible to do it at this code?
If so, how to do it?
Thanks.

This is my code:
https://code.sololearn.com/WhW952GG7FDO/#html

Answer 1

you have to use the <style> tag for that

Answer 2

<link rel="stylesheet" type="text/css" href="filename.css" >
put it in head section,
I assumed that you're asking to add external css file in html.
let me know if your query is something else