To run the applet, the following zip file needs to be downloaded to your PC. Then extracting it will make a folder with the applet file in it along with a text file that contains the acceleration data. Now just double click on the .CDF file there and this will start the applet.
You might see a warning message at the top first time you start the applet. Simply click on the button at the top right corner to enable dynamics. That is all. This message is harmless. Here is the zip file HWs/HW1/CEE_744_applet.zip
Here is the data file HWs/HW1/free_vibr.txt