audicity plug in
 

I am editing sound from videoclips in Audicity. I mainly want to remove a hum in the sound. I can do it with Nyquist Prompt but it'll be more comfortable with the Notch Filter Plug-in.
I have downloaded the Notch Filter Plug-in for Audicity and as described on a help page in wiki (Noise Removal - Audacity Wiki) I copied it to the plug-in folder in Audicity. But it doesn't show up in the effect drop down menu! Did I miss something?