When you download a plug-in from the free trials page it arrives as a .zip file.

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​Right-click on the .zip file.

Choose Open With > Windows Explorer.

(If you’re an advanced user, you can also use your favorite decompression app, like WinZip.)

​You’ll get an unzipped folder.

Quit Photoshop and re-launch it.

The plugin is now installed. To use it,

Open any RGB-mode image and select an area.

From the menus, choose the plugin you want to use.

​If the Filter menu is greyed out, it's because your image is not in RGB mode. Change to RGB mode and it should work.