Oh, sorry - I didn't see your question right away. (You will get a much faster answer by sending me an email. You will find my email address at the top of the source code as well as in the help file.)
> >> plt > Not enough vectors to plot
Ok, you typed plt with no arguments which means it goes into its "workspace plotting" mode. But this means you must have at least two variables in your workspace. (one for x and one for y). If you type "who" it will show what variables you have defined. (It will probably show that you have not defined any). Assuming you actually do have some variables defined, when you type plt a window will appear listing these variables and how big they are. Then you can pick which variable you want to put on the x axis and which variables you want on the y axis ... then click the plot button - and the plot is created!
> >> plt help
Ah sorry - this is really set up by default for Windows based systems since the plt.chm file is included. But not all operating systems can read chm. (You can try opening plt.chm from your file manager to see if this works). For a non-windows system you should unzip the file "html.zip" which contains the html version of the help system. (Be careful to preserve the directory structure included in the html.zip file. After unzipping this file you should be able to view the help by clicking on "plt.htm" or by typing "plt help" at the matlab command prompt.