Unzip downloaded files.
Store the actions and gradients with like files in the Photoshop application folder.
On Windows, the action folder is usually C:\Users\your_user_name\AppData\Roaming\Adobe\Adobe Photoshop version\Presets\Actions
The Gradient folder is in the same vicinity.
To install Photoshop actions drag the .atn file to your Photoshop window.
To install Photoshop gradients drag the .grd file to your Photoshop window.