Playing a preset action in Photoshop

To play a preset action, just open the file you want to apply the action to and then do one of the following:

-->In List mode, select the action you want to play, or expand the action and select the step you want to begin with. Then click the Play Selection button at the bottom of the Actions palette. You can also choose Play from the palette pop-up menu.

-->In Button mode, click the action you want to play. There are no other options.

If you want to play back just one step of an action, say, for testing purposes, select the step you want to play in List mode and then Ctrl+click (Ô+click on the Mac) the Play button in the Actions palette. You can also simply double-click the step in the list while holding down the Ctrl key (the Ô key on the Mac).