Hello, @heffernanj,
Students will be able to navigate to Chapter 1 if you assign unit 2. As per the post below, assigning a unit just designates that unit as the first one students see when logging in. Here is some more information on that. How do I assign mutlipe units at once?
Personally, I put links to the activities and units I want students working on in my content management system (Canvas), but there are a lot of different ways to handle it.
Hope this helps!
Mike