ACX Check plug in

I have downloaded the ACX check plug in but do not understand how to get it into the Audacity program. Please help. I am not very skilled with computers so any instructions that you provide will need to be very simple. Don’t be shy about making them idiot-proof Any help would be sincerely appreciated.

The ACX Check plug-in is a “Nyquist Plug-in”. Installation instructions are here: http://manual.audacityteam.org/man/effect_menu.html#nyquist_effects