That's rather prominently displayed on their website:
http://www.fit-pc.com/web/about-us/contact-us/. You can see a list of current resellers there also:
http://www.fit-pc.com/web/purchase/resellers/. I don't know what requirements you need to meet in order for them to consider working with you; but I imagine at the very least you would need to be a registered business with your chamber of commerce, you would need to know your country's import regulations and duty fees, you would need probably to have a business plan with expected number of sales per month and plans for expanding on that, and so on. Well, at least that would be what I would want to see.