As already posted, you can either get it online (go through the link in the member's website) or you can call MS.
My advice is to call MS - the CM will make the process very easy and you will get a voucher. You can use the numbers on the back of the voucher to make a Best Rate reservation online (I did) and to buy a DDE (I will do this later).
FWIW, I did try the ticket website several times and found it very frustrating. In fact, I ended up calling ticket services twice to make sure the transaction wasn't processed more than once. Turns out it never went through at all either time. Needless to say, I was very frustrated with the website and was more than glad to let MS handle it for me.
IMHO, Disney's websites (in general) are not very reliable! I had trouble with the BR site, too but was able to eventually get it to work. It took multiple tries, though. Maybe it has since improved. My experiences were in late July.
Best wishes -