2006 Honda Civic Question: How do I find out what part to order to get the back window in to come down?

The electric back window on the driver's side in my car will not come down. This window has been like this for about 3 months since numerous tries to get the window down have been unsuccessful. I have purchased a switch for the back window and one for the driver's window. But, neither of these worked because the window still will not come down.