light help: can't see the dotted lines !?

[blood2.0]

i am trying to learn how to use light but i dont have the helpful lines like the one in wikipedia how do i get them?
wikipedia

Mine

[Odin]

In your preferences window, enable "Show Light Radii." It's in one of the tabs. I forget which one.

[Divmax]

Press "P" to go into Preferences.
Go to Display > Entities
Check Show Light Radii

[blood2.0]

thank you