If your instructor has asked you to copy an assignment from a Google link and add it to a Group Discussion, Page, or other area for the purpose of collaboration, here's how you will accomplish the task:

Access the Google link. If the instructor has created it as a "copy" link, you will simply click copy and it will automatically save in your Google Drive. Otherwise, you can copy and paste the information (Mac=Command 'C' for copy; Command 'V' for paste/ Windows PC=Control 'C' for copy; Control 'V' for paste) from the instructor's page to a new document in your own Google Drive folder.
You may need to authorize Google Drive in Canvas to make sure it shares in the right place. (See how to authorize Google Drive)
Find the document in your Google Drive.
Access the "Share" button in the upper right side.
Access the Advanced Settings
Access the "Change..." settings.
Change the link to be open to edit by everyone with the link by clicking the appropriate button, finding "Can edit" on the drop-down menu, and clicking "Save ".
Copy the "Share" link.
Go back to "Groups" in the global navigation at the left side of your Canvas screen and find the group in which your instructor wants you to work.
Access the appropriate space (Discussion, Page, etc.) from the left-hand group navigation menu.
Add a new item (Discussion or Page). Give it a title.
In the content editor, create a title, add the descriptive text and click on the link icon.
Paste the link and click "Insert Link."
This will create a link where everyone can access the document.
Alternatively, if you'd rather embed the document (which gives easier access but restricts some of the view and workspace),
1. find the "V" app icon and click "Google Apps." (You may have to sign into your Google Drive if this is your first time. Use your Chapman credentials to do so.)
2. Find the file and sScroll down to click "Embed" at the bottom of the interface.
3. This will embed the file like the one below: