I created a new database template. But, there's some stylistic things on that page that I'd like to do with CSS. 

I noticed that inside of Templates there is a CSS tab, and no files inside. I created a CSS file there. 

How would I go about assigning that particular CSS file to my new database template, or that file to specific divs?

I guess it would need to be called in one of the theme's HTML files... but what is the location of the new CSS file I created?

You assign it in the settings for the page, the database was placed on. No coding necessary:

 

I'm loving 4.1 more and more.