When you join you'll start off on the verification page, read over the introduction, rules & then tap the green ✓ emoji to unlock the rest of the server.

In the introduction category, there is a page called "Welcome" look for your welcome card and view the brief manual in your card to learn how to get started in the server.

ⓘ  There's also a "New to Discord?" page in the introduction category that will teach you where to begin & how to use certain features in the server.