Pls consider additional sources on the bottom of this entry
to associate your dropbox folder with a grading items, go to your dropbox module
select the dropbox folder and click on edit folder
scroll down and choose the grading times, which needs to be associated with that folder.
Grading a D2L Dropbox with a Rubric http://www.youtube.com/watch?v=VP-_RNiRV-k
D2L Dropbox: Creating a Dropbox Folder