@amisfitlife,
How do I add a file to a group?
From your News Feed click
Groups in the left menu and select your group.
To the right of
Write something... click
More > Add File.
Click
Choose File to select a file from your computer or Dropbox.
Choose to say something about your file and then click
Post.
Keep in mind links to Dropbox files can be shared outside of the group.