Have you followed everything mentioned in the video tutorial about how to install? Part 1 is about installation.
https://discuss.eroscripts.com/t/how-to-script-in-openfunscripter-video-tutorial/16637
I also recommend that you use the search tool here since this question has come up before. Check if those threads might help you further.
Make sure you are using the right downloads. You are mentioning both OFS and JFS in your post. These are two completely different software and have different installation procedures.