As far as I know, there's no way to do that. Publishing from a file creates a new arc, so you'd have to take the existing one down to effectively replace it. (Note in case you're new to this, that's almost certainly not what you want to do, as unpubbing the existing arc loses all its ratings and related badge progress.)
Blue
American Steele: 50 BS/Inv
Nightfall: 50 DDD
Sable Slayer: 50 DM/Rgn
Fortune's Shadow: 50 Dark/Psi
WinterStrike: 47 Ice/Dev
Quantum Well: 43 Inv/EM
Twilit Destiny: 43 MA/DA
Red
Shadowslip: 50 DDC
Final Rest: 50 MA/Rgn
Abyssal Frost: 50 Ice/Dark
Golden Ember: 50 SM/FA
First thing you should do is use the My Creations-->Published Stories tabs then click on the Edit buttom.
When you're on the final page of the mission creator there are icons on the top-center-left of the page. One of those icons is to Republish and Exit or something to that affect.
After editing your single mission or story arc, you click on that icon on the final page, your mission/arc will be republished with the changes you made.
There may be a 5 to 10 second delay on your story/mish getting republished.
That was it, thanks!
I notice that screen also gives the option of saving your published mission as a local copy as well. In case you didn't keep the original.
Right. What I was describing (and what you had asked) was how you can't republish from a working copy on your local system. Looks like milehigh answered what you were looking for, which is how to edit an already published arc.
Good luck. 
Blue
American Steele: 50 BS/Inv
Nightfall: 50 DDD
Sable Slayer: 50 DM/Rgn
Fortune's Shadow: 50 Dark/Psi
WinterStrike: 47 Ice/Dev
Quantum Well: 43 Inv/EM
Twilit Destiny: 43 MA/DA
Red
Shadowslip: 50 DDC
Final Rest: 50 MA/Rgn
Abyssal Frost: 50 Ice/Dark
Golden Ember: 50 SM/FA
[ QUOTE ]
That was it, thanks!
I notice that screen also gives the option of saving your published mission as a local copy as well. In case you didn't keep the original.
[/ QUOTE ]
Be careful. Once you hit the "save to local" button, you are working on the local copy. That means the republish option vanishes.
What I do is edit the published version, republish it, then open it to edit again, and hit the "save to local" button. That way I get the new version up to their server and here on my machine.
Avatar: "Cheeky Jack O Lantern" by dimarie
I have a published mission. I've edited the local copy of the published mission. How do I republish it? I'm not seeing a Republish button anywhere.
I've searched, but my search fu sucks.