Invoices and credit memos are emailed to the main email address on your account as soon as they are created. However, if you require a copy you can access it through your control panel.
After you have logged in select Account from the top menu.
Now select Financial Documents.
You'll see a list of invoices and payments on your account. Find the invoice you require a copy of and click it. Select Download PDF to save a local copy to your computer.