Several people who are new to Photoshop actions have written to request information on how to use them. The PDF link below will open a PDF document in a new window that explains how to load actions into Photoshop, and then how to run or "play" the actions once they are loaded.
Below is a link to an actual Photoshop action that you can download for practice. When properly loaded into Photoshop and run, it will create a new layer at the top of the layer stack, fill it with 50% gray, and change the blending mode to Soft Light.