Question

I found a mistake in
http://docs.webplatform.org/wiki/tutorials/traversing_the_dom
DOMTree0.gif is wrongly posted that it is not belonged to the topic. I
illustrated a new one, but when i uploaded the PNG file, it said "You do
not have permission to create new pages."
How can i upload the PNG?
I am newly registered, and it's my first time to edit the doc.