How can I style my tracking page such as fill-up and button. Tried last year resolution didn't work.

[KyawZawLin]

Last year's resolution was to put a section of CSS code. Case link - https://community.shopify.com/c/shopify-design/how-can-i-customize-css-for-my-order-tracking-page/td...

I have put the code at the bottom of the code in base.css but mine still looks like this. 

I would appreciate your help here. thank you.