Once you have downloaded and unzipped your Action, place your Action in a common folder.

Once you have established that folder, open Photoshop, open the Action palette, click the small triangle in the upper right hand corner to access the fly-out menu, then choose LOAD ACTIONS.

Using the file dialogue, navigate to wherever you have placed your Actions. Click the Load button in the file dialogue, and your Actions will appear at the bottom of the Actions Palette.

You can also drag and drop Actions onto the Actions Palette in Photoshop. For most Actions, it is best to start with a flattened RGB 8-bit image.

After loading Action, open any of the 36 PNG files, then run Action. It will build layers that can be used for masking with strokes and so on. Use whatever layers you want or turn off. Second action changes black to white or white to black.

How to use template:

Click on bottom layer. Paste your image above bottom layer. Rotate and size behind mat openings while holding shift to constrain proportions. Zoom in to make sure green does not show. This ensures your image is larger than the opening.

To add a texture into the background or edge effect, make a selection of the black or white areas of that layer using magic wand, with contiguous unchecked, then go to menu edit>paste into. Rotate and size behind mat openings while holding shift to constrain proportions.

See Gallery example of the 18 different combinations that can be created with one template:

http://mikedubu.smugmug.com/gallery/3992804#232183230