Shadow Customization

Hi there,
I′m absolut new to WP and trying to run a simple blog. But, i like to edit some visual stuff before use. I′m using Titimplik theme from https://wpcharity.com/ .

You can see my blog here: https://www.blogdoaero.com.br

I want to change the default shadow to something like this one here:
https://themefuse.com/wp-themes-shop/

I try some shadows using this site here:
https://www.wordpressthemeshock.com/css-drop-shadow/
and copy/past the code to “Edit CSS” but nothing happens. How to make it work?

Thanks for attention!