Turnitin.com only allows one instructor per class. There are two ways around this:
Unfortunately it's not possible to remove a paper from the database, but TurnItIn accommodates such papers by allowing you to create a "Revision Assignment". From the Penn State TurnItIn FAQ:
Q: Can students submit multiple drafts of an assignment without having the drafts compared against their previous submission(s)?
A: If your students have already submitted their papers to an assignment and you want to let them submit another draft, you can create a revision assignment. When a student submits a paper to a revision assignment, the submission is not compared against the student's previous submissions.
To create a revision assignment:
Click the create a new assignment link. On the assignment creation page, choose revision assignment from the create a new: pulldown menu at the top of the assignment form. Choose a paper assignment using the based on paper assignment pulldown menu on the revision form. The revision will be added to the assignment you have selected. Click the submit button to add the revision to your class homepage.
Alternatively, when you are looking at the Originality Report for a paper, you can remove from the report any source that you know is acceptable -- in this case, the student's previous submission of the paper.
Since the introduction of GradeMark, when you print an Originality Report, TurnItIn will create a report that is formatted to look like the student's submitted paper, with matches marked in grey and numbered to refer to matching sources. However, many instructors find the new printed version of the reports less usable for distinguishing between multiple sources of potential plagiarism.
You can still print the old-style Originality Report: When you are viewing the report, click "Text-only report" in the lower-right corner to switch back to the old TurnItIn Originality Report style. If you then click the Print button, you'll get the old-style report format, which you can print out.
You can then switch back to the new viewer by clicking the "Document Viewer" button in the top-left corner, under the TurnItIn logo.
Even to test one paper, you need to set up a class and create an assignment. Once you've done that, click theSubmit Paper button in the assignment Inbox.
After you submit it, the paper will be listed in the Inbox. After about 10-20 minutes, the Originality Report will be added.
Note that the paper you submit must have been typed, or processed with an Optical Character Recognition (OCR) program to produce typed text. Scanned images are unusable by TurnItIn.com
If you plan to submit a paper you are scanning, you can use Adobe Acrobat's built-in OCR to convert them to text that TurnItIn can read. Acrobat Professional is available electronically from Software Distribution, and physical copies are available from the bookstore.
When you are creating your assignment, you can allow it to ignore any matches to texts propetly cited in MLA, APA, Chicago, or Turabian format. Click on More Options and check Exclude quoted materials from Similarity Index for all papers in this assignment.
TurnItIn won't allow you to change this setting for the whole assignment after the first paper is submitted. If you forget to check that option while setting up the assignment, you can only exclude cited matches for each paper as you review it.