How do I find things in Canvas?

The menu on the far left (blue bar) is the Canvas navigation. To find a course you're enrolled in, click "Courses."
Once inside a course, the left side menu (blue text) is the Course navigation menu - that's how you find things within a specific course.

How do I know when something is due?

An assignment's due date is on your Calendar, is listed on the item in Canvas, is shown from the Modules page, and assignments are listed by due date at the bottom of the Syllabus.

The syllabus for a course can be found by clicking "Syllabus" in the course menu.
At the bottom of the syllabus, a list of assignments is shown with their due dates.

The assignment submission page should be in the Module. To submit, click the blue button at the top right that says "Submit."
The assignment submission page will tell you the due date, how many points it is worth, what type of submission (text only, uploading a file, etc.), and how many attempts you're allowed to submit.
The assignment submission page will also have assignment details your instructor provides, and a rubric if one applies to that assignment.

The assignment page in Canvas contains information on the date, points, type of submission, and the number of attempts.

To find lessons and get started on readings and assignments, click "Modules." Find the module (for instance: Week 1 or Lesson 4) that you're looking for, and click on the first item in that Module.

Arrow pointing at the first item inside the Lesson 1 module

From any page, assignment, or item in a Module, you can click "Next" at the bottom right. The "Next" button is how you move through lesson contents.

The Next button is at the bottom right of the screen

If you want to go straight to something in a Module (for instance, if you're ready to take a quiz) you can click "Modules" and then click on the item directly.

screenshot highlighting how to directly navigate to a module item

This Canvas Student Guide is organized by topic, and answers almost any question you can think of, with step-by-step instructions.
These Canvas Student Video Guides walk you through most everything you'll need to do in Canvas.