Choose Edit > Fill. In the Fill dialog box, for Use, choose Pattern, select a pattern from the pop‑up palette, and click OK.
If Pattern is dimmed, you need to load a pattern library before you can select this option.
Select the Paint Bucket tool . In
the options bar, choose Pattern from the Fill pop‑up menu, and select
a pattern from the Pattern pop‑up palette. Then click to fill the
selected area with the pattern.