The video below will walk through the process of opening assignments in Apex and how to add your content to them.
There are three options discussed:
1. Using Kami to edit PDFs - Help Desk Link on Installing Kami
3. Using Google Docs and copying worksheet content to blank google doc
Two options for viewing this video are below, the first is stored on the google drive if you don't have access to YouTube, the second is linked to YouTube