How to Use Civilization IV's Worldbuilder

Whilst in a game Click "esc" for the Menu. (Ctrl 'W' works as well.)

Click on- Worldbuilder

(Here you can do "Anything" to customise the World you are on)

Go to the top Tool-Bar, and search for "All Tiles" which enables you to transform the entire world into either Grass, Hills, Mountains, or Ocean.

Select "Ocean"

If you end up with thousands of Waves, select "Add all Grass".

(This is best for Duel-Standard Sized maps)

Then browse' the Toolbar and search for "Terrain"

Click on the Ocean Tab/or/Button

Then hold the mouse button and go over "ALL" of the land

Now you will most likely end up with weird circles. So-

Go back onto the "All Terrain" button from earlier on in the "How To-"

Select "Ocean"

Now customise the world to your liking!

You may also use to grant yourself any free technologies or edit your cities top put every world wonder in it so you get the upper hand