You will receive an email approximately 2 to 3 hours after the auction closes.
Go to My Accounts
then go to Invoices
or access your invoices directly here.
You can also go to My Bids, Show Closed Items and sort by Bid Status (or choose the filter by Auction option).
You can access My Bids with the Show Closed Items and Bid Status order directly here.
Looking for invoices before November?
Answer to a related question: Did an item sell for the amount you bid on, but you didn't win the item?! See here why.