World in Conflict needs to be updated up to the latest patch for WICEd to install. Once this is done, open WICEd and select "New Map". Now, you can take a look at all the sky and ground themes that you have available. We're going simple for now, with a rural American Midwest themed-map, so select "clearsky01" and "greenhills".
Name your new map something without any spaces in it and then select "Create". The editor will ask you about two Generate boxes at this point. Check both, and then go have a coffee. This process will be time consuming, so be patient. Once the generating is finished, you should be viewing the empty terrain of your new map. You can move around your new map by holding down the right mouse button, while you move the controller toward the part of the map you want. You can rotate the camera by pressing and holding the middle mouse button and scroll the wheel to move up and down.
At this point you can begin playing with the terrain. You'll find six buttons in the toolbox called "Terrain." For fast and dirty editing the best thing to use is the "Pinch" tool. Choose the "Pinch" tool and move some terrain around to see how it works and feels in your hand. Select the brush size you want to use from the drop down list located at the top left and then start changing the terrain. If the terrain texture isn't what you want for the terrain you're making, don't worry about it for now, we'll take a look at that part later. You can make steep terrain, but don't make it too steep. If you want to smooth it out a little, go over it with the "Smoothing" tool.
At this point, were going to make a road to fight over. Select the arrow in the toolbox to open the "Object Editor" window. Once the window appears, click the little road icon in the middle of the window. Under the Available tab below, there will be a list of road types. In this case, choose "Countrysideroad", and then position the blue dot on the terrain where you want the road to begin, and then left click. A starting point will appear, then you move the mouse to make a section of country road and then left-click to create.
Play around with this until you understand what you're doing. Notice how the ground automatically flattens to account for the road you create. Once you have the roads the way you want it to be, click the arrow in the toolbox to turn off the make road mode. To confirm your road, select the "Lock Road" button in the Object window, and then answer yes to the question that appears. Once you have the road in place, don't alter the land beneath or near the road now, or the road will be misaligned, and vehicles will run off the road.
Now, choose the house picture in the Object Editor. You will see a long and disorganized list of objects for your map. Select something that is appropriate and left click on the spot you think the object should go. If you want to turn the object before you put it down, press down the left Ctrl button and left click. Should an error message show up, just move onto the next object on the list. If you're placing down a building on the map, make sure at least one door to the building is left unblocked. When constructing a multiplayer map, don't choose anything from the Dummy, Single Player, or Civilians folders.