Community Settings allows you to control the look and feel of your Community through Branding, Landing Page, and email customizations.
To access Community Settings, go to the Admin > Community Settings. You'll see a dropdown that brings you to the following customization flows (depending on your Community Settings):
The first thing you'll want to familiarize yourself with is Branding. If you haven't yet customized branding for your Community, see our Branding and Site Look article in Getting Started here.