Go to http://www.softronix.com/logic.html and download Multimedia Logic and install it on your machine.
Using the help facility, read (to understand for future use) all the help on the system.
Create a 1- bit adder (takes two input bits, A and B, as well as a carry-in bit, and outputs a sum bit as well as a carry-out bit).
Turn in a printout of your circuit and email me a copy of the .lgi file (the type you get when you save a Multimedia Logic file).
Next, duplicate your 1 bit adder and make connections to make a 4 bit adder.