This feature allows you to use DirectX plugins to apply effects to the audio you are working with in WavePad. To use this feature, select Effects menu -> DirectX plugins, and in the window that appears you should see a list of DirectX plugins detected on your computer. Pick the effect you want to use, and click the "Settings" button if you want to change the configuration settings around. Next, click the "OK" button to apply the DirectX effect to your audio.