re-read the details. it says be creative and go outside the box so its whatever you want. the real question im wondering is about how many entries. i got the feeling it was one per person but many are uploading several. it wasnt' specific so who knows. also a lot of people aren't doing them as attachments. we'll see if that effects the judging.
to answer the other question you dont drag and drop you go to the bottom of your post response page and there should be a button that says manage attachments. click it and go from there. good luck