pulse function

I am trying to set up my arduino to read frequency from a function generator and display it on an lcd and want to use the pulse function. the outputs are square, triangle and sine. how would I go about interfacing the frequency and writing code? I tried the reference on this site but dont understand it. can someone help me?

there seems to be a library: FreqCounter.h

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1272558914/25

i dont know how accurate it is...

-arne