SMBX HELP WITH GAME UPLOAD RELATED STUFF

First off, I know this particular question has been asked and answered before, but I can't find it! Rage... Anyway, yeah, how do I upload an SMBX game on this site? Assuming, of course, it's been accepted. Also, could I make and upload a very short game (one world, seven levels) mostly to get feedback on whether I'm good or horrible at designing Mario levels? How to conclude... I hate conclusions... So, yeah... That's it. Any help would be greatly appreciated and thanks in advance for helping a newbie!

Thanks for the tips! I guess Mario's Little Land won't see it's debut... Quick question. Would it be lazy to use this thread as the request thread you mentioned? I probably shouldn't even ask that because the answer is obvious...