FA.nrrd is an example that was used in old templates. Please use the latest module template.
You can use any test data - from Slicer’s sample data sets or anything that you upload into your own repository.
I’ve already described in a different topic how to run apply method of Local threshold effect. If you still have problems with that then please ask there. Provide link to your source code, if you have questions about why your code is not working.