Say you want a nice soft glow in the background of your title page.
Do this. Draw a square.
Click Gradient from the Window menu
Then click the gradient button to apply a gradient to your square. And then select ‘radial’ to make it spread out.
Now the trick with making it spread out, it to press ‘g’ and then manually drag the end point of the gradient meter out beyond the square.
Once you learn how to do that, you create create pretty much any gradient you want. Just grab the gradient tool, move it around, and try different things out.
Links that help
If for some reason you find the gradient tool isn’t allowing you to change the gradient (i.e. pressing ‘g’ and then locking you out…toggle the fill stroke switch in the gradient window.
Chances are you have stroke activated when what you really want is fill (or vice versa).