After placing an order, you should receive 2 e-mails. The first is the order confirmation, and it will have a subject that says "Order #XXXXX confirmed". There is nothing actionable in this e-mail.
The 2nd e-mail you will receive is from Customer Services <customerservices@bsimerch.com> with a subject "Your download for Underworld is ready", and this will contain the download link to the file.
Underworld changed e-commerce platforms from Townsend Music to Shopify when the Drift Series 1 Complete box launched, so your old account info won't work. If you want to sign up for a new account on the new store, use
this link.