Many Photoshop plug-ins have an automated installer which adds necessary data into the registry or places the files into the folder of the software. In case you have plug-ins which are standalone (.8rb, .Plugin, etc) then you should copy those files (please note that Photoshop should be closed at that moment) into the following folder: \Program Files\Adobe\Adobe Photoshop CS5\Plug-ins. The next time when you will open the main software, these plug-ins (if are compatible) will be loaded into the application and then you will be able to access them from the main window of the software. The plug-ins will be accessible from the Filter menu.
