Ok, so, here's the deal when you want to submit to the club. You have to upload it to your own gallery first, then you can submit it to the appropriate category. Pretty much like you would have done before the conversion of the club (it's certainly what I was doing anyway). And that's what is highly recommended you keep doing, because if you click on "Submit" while on the club itself, the website is going to take you to submitting an image in your gallery anyway and not even give you any club category options until you go back to edit it after it's been put into your gallery to get the category options. You're better off simply putting it your gallery from the start then submitting like you would someone else's deviation.
However, I'm seeing some folks who are just dumping their submissions into the first category they find, which has been the Aliens category. They're throwing written deviations, humans, ships or weapons into the category, likely hoping that they'll get moved to