To exclude the match:

1. Open an Originality Report
2. To exclude matches for a top match hover over the match you would like to view the underlying sources for and click on the blue arrow icon that appears.
3. To exclude matches from the "All Sources view" click on the "All sources" icon at the top of the side bar
4. Click on the "Select Sources to be Excluded" button at the bottom of the sources list to enter source exclusion mode
5. Select the sources that you would like to remove by clicking in the check box next to each source
6. Once all the sources are selected click on the "Exclude (#)" button located at the bottom of the sidebar to exclude the sources

source: http://turnitin.com/en_us/training/student-training/viewing-originality-reports (view this document for additional information on how to interact with your TurnitIn report)

Note that if your mentor, dissertation committee member, or another individual at the University submits your document to TurnItIn, your current work will still match to your previously submitted document (once it is in the repository it cannot be removed) and therefore you may be asked to explain the match.