Hi Anusha,
Please follow the below steps to re-submit your assignment:
1. Please access the link "My assignments" which is on the top right of the Window.
2. All your assignments will be listed in this page, please click on the assignment which your are required to re-submit.
3. Upload your assignment again the same way as you have been doing before.
Hope this is clear.
Cheers...
Java Teacher
May 24, 2010