FWsim loads effects from “Documents → FW-Sim”. There, you will have one subfolder per author name. You can also arrange your effects files differently and group them by subject, for example. So when you download effects you could put them into a folder “Documents → FW-Sim → DFWST” or “Documents → FW-Sim → Effects I downloaded from the FWsim community forum”.
you have put the effect file into the right folder, so it should work. Let’s investigate why it doesn’t:
Do you get any error message when FWsim starts?
After putting the file in that folder, did you restart FWsim?
The current beta version 3.4.1.308 is a preview of FWsim 3.5. So it’s “FWsim 3.5” even though the version number still starts with “3.4”. The version number will be increased to 3.5 once testing is complete.