I'm not familiar with the download coupons that you mentioned. But if they allow you to download songs, I can tell you how to transfer them to the B2 after you've downloaded them to your computer.
There are three ways to transfer music to the B2:
1) Import from a USB disk plugged into the B2's USB port (either A or C). The USB stick must be formatted as FAT32 (no other format will work).
2) Upload via the WebUI.
3) Direct tranfer from your computer to the B2 when it is set up as NAS (Network Attached Storage).
In all cases, the music must be arranged in a folder structure where the Artist folder contains the Album folders, which each contain the song files. Artist\Album\tracks.
The Brennan website is effectively the manual. The advantage over a paper manual is that new information can be added any time, and can be updated as needed. Most of what a user needs to know is on the website. IMO, every new owner should spend time reading the information on the website. Before I received my B2, I spent over a month reading the website and hanging out in the forum reading about how to do things, and about problems and how to solve them. There are a bunch of us here who are happy to help. Different ones of us explain things in different ways. Hopefully, one of those ways will make sense to you.