You can´t because they are a scam. They are only selling a few devices to shut up false accusations, mainly sending devices to press as fast as they can, so they get nice reviews about how this things work, because in 1 or 2 months, they will generate 0 bitcoins.

They are a scam for this reasons:

1. They accept money on a device they did not even build yet.
2. You could wait 1 year or forever to receive it. With mining time is everything, the more time goes on, the less value your device. By the time you receive it, it could hardly even make your ROI back.
3. Amazon and every other vendor, including Sony with pre-orders on PS3, just to name one example. Only and ONLY charge the pre-order once its shipped.

This guys charge you money upfront for something they don´t own or have. And since there are not refunds, you paid AIR. Nothing.

Its a very elaborated scam. This is the reason why they are so secret about who is behind the company. Most pre-orders where used to fund themselves, and they are probably indirectly using that hardware to mine bitcoins, with that profit they though they could probably generate money to create more hardware, and basically making hardware for free. This is why Bitcoins are plumping in price.

Its going to blow up very soon, once bitcoins start to get lower and lower, as this ASIC vendors try to mine more and more, to produce their own hardware, which are supposed to send to customers. And since most customers actually never paid with real money, most with Bitcoins its like a big ponzy scheme they created without knowing.