I’m not sure how much experience you have with Magento, but it’s a real beast learning how things work together. First off, don’t use their theme upload extension because you don’t need it, but most importantly because it’s not working correctly and has been decommissioned.
I just took a look at your link and it seems you don’t have Magento installed correctly, or possibly some files have been deleted/replaced with your recent upload. I’d be happy to help you get started, but I’d need ftp access and db info, which you really should only be giving to HT (I don’t work for them although maybe I should).
Hit me up at kevin leave-this-part-out at woolf dot com if you’d like me to help you. The instructions would be too involved to post here on the forum, but you can also check out the Magento site for lots of tips.