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If the category is actually accepting submissions, then you'll see an information page titled "Submit a Site to the Open Directory" (that you should read) with a button at the bottom to click to agree "I have read and understand the submissions guidelines, and I'm ready to submit my site" -- that will take you to the actual submission screen..
Hope this helps.
The category you mention has been renamed and/or moved elsewhere, so that's why you can't submit at this point in time. I suggest you wait until the upgrade is done before trying to resubmit.