There are a few standard things we will go over real quick for when you are inside a campaign.
Along the left is your main campaign navigation. This will take you to all the main sections for building out your campaign world. Your campaign name will always be at the top of the left navigation in case you join multiple campaigns, you can quickly see which one you are currently in.
The main bar along the top of the content area will always contain the title of the current screen and generally some main buttons that go with that screen.
The main content area then consists of what we call "panels" that hold different data. Each of these panels has a title and may also have a small button(s) that pertains to that panel data.
Important links within text content will be orange (on the default classic theme) or some other bright color. Less important links will be the default text color but with a dotted underline to make them more visible.