Hello Claire! I hope I did understand the question right:
How to upload: to upload an image in the Monthly Shooting Asighment (you can see this gallery down on the page) : Choise your picture and then push the edit button, press te "'All subscriber galleries", you find a drop-down menu and press the Monthly Shooting Asighment,thats it. Its only for fun!
I have made a copy of the text made by Film Sprocket some times ago about the MSA idea, here it is:

For any new readers, here's the basic idea of the MSA :

1. Take note of the MSA assignment, which will be inserted into the title of this thread.
2. Take your photo(s) according to the assignment guidelines. Try to shoot something new rather than grabbing from your archives.
3. You can post your photo in the MSA Gallery: http://www.apug.org/gallery/showgallery.php?cat=508 , or, you can host your photo elsewhere and link to it in this thread, or, you can post it as an attachment to a message here in this thread and it will show as a clickable thumbnail.
4. It's all for fun, there are no prizes, but at the end of the MSA, a previous winner will choose a new assignment and a new "victim" to lead the MSA in a couple of months time (it's not really monthly ).

Hope to see nice pictures here.