Below I will show you how to graphically convolve two signals.  First I will do it with pen and paper, then I will do it with MATLAB.

Now I will show you how to do the same thing with MATLAB.  This code was written by Commander Welch at the Naval Academy.  It is located at this web site.  First you open a new M-file.  You paste the code into the M-file editor/debugger.  Make a directory in your Matlab directory called working. 

Save your code into a file like above. 

Now you need to go to file>>set path and set the path to the working directory. 

For our current set of two signals, we will need the following inputs.  It produces a very neat collection that includes your two input signals and the convolved output.  I think that if you look at the code for a little while you will be able to see how you will need to modify your inputs to accommodate any new signals you might have.  If after you look at it awhile you still are having trouble with it, let me know and I will explain it to you.