How can i make my own worldmap?

[Hellas Man]

I have a problem.I start a game in worldmap(with18civs)and i want to change positions of the civs(and some other changes).I go into worlduilder and i can't change any parameter axcept the place around of that i have discover.If i discover all the world i can interfere in any place(of world map)but i will start the new game in the date i have saved the worldbuilder.

So if anyone knows how can i make a right worldbuilder i please him to tell me.Thank you.