Click the test data download link found on the JDTI download page. You will be able to see this page after you are given access to the JDTI download. Download the zipped package of test data and unzip the contents.
Copy TensorDirections.txt and save it in the main ImageJ directory.
Open the test image data (test20050901.tif) in ImageJ.
Open the test macro (JDTItestmacro.txt) in ImageJ.
Run the macro (click on the test image data which makes it active, then click on the macro and press Control-R).
The resultant images should match (i.e. ADC = ADCtest.tif, FA = FAtest.tif, etc.).