If you go to your list of "Published arcs" and click on an arc, you can see the option to Edit an arc.
Do this and you edit the arc currently on the live server, not the one on your machine. Instead of saving, you have the option to Republish, which uploads the edited arc. You retain your arc ID and your votes this way.
"The Hamidon is a what what of what?" - Brian the mission guy.
Thanks for the reply 
I was wondering if it is possible to alter what a custom character looks like after the arc has been published?
I ask this becuase I plan to alter the apearence of my chief villain in the arc iI'm making when the magic booster comes out, so I want to know f I make the changes after publication, will the changes take effect on the arc?