To import the action, drag the .act file onto your Photoshop app icon, or in the Window>Actions panel, use Load Actions in the three-bar menu.
To import the gradient presets, drag the .GRD file onto your Photoshop App icon, or in the Window>Gradients panel, use Import Gradients in the three-bar menu.
The action creates the light rays effect based on the light/dark values of the entire image, so no need to have any specific layer selected. Check out the tutorial above for some ideas and examples of how to put it to use!
.GRD gradient presets