In UT3 adding a basic light is quite simple(Because basically you just need step 1 and 2.).
To do this you will need to have a subtracted space ready.
1. Right click inside your map. (Where you want it, or move it around later)
2. At the menu that you get open click
Add Actor - Add Light (point)
3. If you cannot see the difference, maybe you always have unlit render view?
Above the 3D view window you will find some small icons. when u hold over them you will see what they do.
By choosing "unlit" you will always see full light in your map. (From the editor view only off course)
By choosing "lit" you will see how the map really looks when you have rendered lightning.
Select the lit view for now as you are adding light for now. When doing other stuff I recommend using lit view(Choose your self)
But if you are having a slow system look for unlit movement to prevent lagging.
Congratulations you no longer need to stumble in the darkness.
If you want to get more Advanced:
To change the light properties:
Right click on the light and select "Point Light Properties"
- Light - light Component - Brightness (This will change the strength on your light)
- Light - Light Component - Radius (This will change the distance before your light is faded away)
- Light - Light Component - Color
Left click on the looking glass on your left.
or Right click on the light color bar(which is probably still white).
Good to know: Grayness will make the lights color weaker. Adding darkness will make the light more dim(I recommend changing brightness for this feature).
Congratulations you can now dance in your disco lights!