Free autotune program?

I need to use auto tune for my voice on a song i'm doing, and I need it free. I've been trying to use the Gsnap VST on the Madtracker 2 program, but I cannot for the life of me figure out how to get it to autotune my voice. I'm looking for a program that isn't a VST thats free and can autotune for me. If thats not possible, or doesnt exist, i'd like an explanation on how to route my voice through the VST