In addition to the default built-in Actions, Adobe allows installing "actions" from third party developers. A Photoshop Action is a computer script that includes a pre-defined set of Photoshop commands. Actions have an ".atn" extension (Windows) and can be installed by copying (or dragging) the file into the "Photoshop Actions" sub-folder of the Photoshop folder as shown below. For example, for Photoshop CS2 it's typically located at: C:\Program Files\Adobe\Adobe Photoshop CS2\Preset (for Windows)
The next time you start Photoshop, select "Load Action" from the Actions tab. After being loaded the first time, the Action will be permanently available from the Actions menu. You may move (drag) the Action into an "Action Set" if you wish to help organize your actions.
