Download your Action. If it is not unzipped (if it still has the .zip extension at the end), unzip it.
Then install it use one of these three methods.

Method 1
1. Just double-click the .atn file and your action will be loaded into Photoshop.

Method 2
1. Open your Photoshop.
2. Drag and drop the .atn file onto an opened Photoshop window.

To make sure that the Action is loaded in Photoshop, check the Photoshop Action Palette.

pic 1 1024x683 - How to install actions in Photoshop
Method 3
1. Open Photoshop.
2. Go to Photoshop Action Palette.

pic 2 1024x683 - How to install actions in Photoshop

If you don’t see it, go to WINDOW and select ACTIONS.

pic 3 1024x683 - How to install actions in Photoshop

3. Click on the button in the top right corner of the Palette.

pic 4 1024x683 - How to install actions in Photoshop

4. Select LOAD ACTIONS and then navigate to where you saved the Action.

pic 5 1024x683 - How to install actions in Photoshop

5. Load your Action.