any macbook users around to help?

i've had my macbook for a couple of years now. when i first got it, i disabled the trackpad so that i could use my wireless logitech mouse until i got the hang of the mac. well, i think it might be time for me to join the rest of the mac world in using a trackpad, at least some of the time, but i can't remember the steps i took to disable.
if i go to system preference and then to trackpad, i can click on what i think is the proper box but my trackpad still won't work.
what to do? what am i missing?
thanks so much.