Uploading a file or photo problem

Whenever I am uploading the file, I am getting the following message :

The uploaded file could not be moved to /home/sumadhwa/public_html/wp-content/uploads/2009/09.

I was suggested to do like this :
Try changing the permissions on the wp-content directory to 766. If you still have problems, try 767 or 777. Once your uploads are working, change the permissions on wp-content back to 755 again and check that everything still works OK.

But I am not getting as to where to change the codes directory to 766.

Please help me