The applet above shows a three dimensional truss. You can view the object from different angles by click-dragging the object. There are three buttons that control most of the features here which should be familiar if you've seen finite element (FE) packages. These control different aspects of the model creation, analysis, and viewing of the results. The Pre - Processor button will open another window with controls pertaining to model creation. The Run Processor button does simply that, it runs the processor. This means it will analyze the currently defined model. If you make changes in the input (through the Pre-Processor), you'll need to run the Processor before checking the results. The third button of interest is the Post - Processor button, which opens a window similar to the Pre Processor but the controls here allow you to view the results.
The README.TXT button has a short description of the input and other details. Be sure to click on the Black + White button if you want to print unless you don't mind using ** lots ** of toner.
It may be useful for you to try the 2D Truss Analysis if you don't have a three dimensional model. It is essentially the same as this but doesn't allow for rotating the object and the input is simpler.