Whereas the Mandelbrot set and other non-Julia fractal sets are defined entirely by their coordinates (which specify their location in the complex plane), the Julia set needs an additional parameter, a seed point (known as a Julia seed) in the complex plane. The Set Julia Seed window lets you easily set that third defining point.
While you can type Julia Seed values into this dialog, the best way to set this value is to Alt+click or Alt+drag in a Mandelbrot window. This lets you easily change or animate the Julia seed value, while the Julia set updates in almost real-time!
Use the Set Julia Seed window to display and adjust the location of the Julia seed for the current Julia window. It also gives you a way to make all Julia seeds currently in use visible on any non-Julia windows that are displaying that part of the complex plane -- they will show up as red "+" symbols.
To open the Set Julia Seed window: On the Location menu, click Set Julia Seed. This command is available only for Julia fractals.
Going from top to bottom the information displayed is:
Fractal explorers rarely specify Julia seed information numerically. Instead, they use the related non-Julia set, the Mandelbrot set for instance, as a map of all Julia sets. Simply alt-click in a non-Julia fractal window, preferably of the same type, to set the Julia seed. If you alt-drag, the Julia set will animate, as fast as your computer can manage. For details on how to optimize the speed and quality of this animation, see the Miscellaneous page of the Preferences window.