Assignments and Documents are not displayed on your Create page - if you'd like to see and manage all the Assignments and Documents in your campus, you'll have to use the Resource Library. It can be accessed from the navigation bar on the left hand side of Coassemble:
In the Resource Library, you'll see two tabs: Assignments and Documents. Naturally, they give you a list of Assignments and a list of Documents, respectively.
You may search for particular resources by typing into the box labeled "Search", and you may sort resources by title by clicking the "Title" column heading.
To access one of the courses containing a particular resource, you can simply click on the course's title. Additionally, when you hover over the resource the below buttons will appear:
From left-to-right: the eye button will preview how this resource appears for students, the notepad button will open an editor so you can change the resource, and the download button will allow you to save a local copy of the resource. The download button will only appear for Documents, as Assignments are not downloadable.