Squarespace Capable of Multiple CSS?

Site URL: https://sphere-plums-byjf.squarespace.com/

Hi there, I'm new to coding. I found a code and uploaded it to Squarespace's Custom CSS to modify the header. I found another code I'd like to use to add a drop shadow to white letters overtop an image but I'm wondering if I can use multiple CSS and how. Please help

Add the new code after the previous code separated by a blank line. That is an oversimplification of a complex technology, CSS.

CSS Ruleset Terminology