Apply an existing gradient to an object
Select an object and do one of the following:-
To apply the last used gradient, click the Gradient box
in
the Tools panel or the Gradient Fill box in the Gradient panel. -
To apply a preset or previously saved gradient, click a gradient swatch in the Swatches panel.
To
display only gradients in the Swatches panel, click the Show Swatch
Kinds button 
and
choose Show Gradient Swatches.