Sorry for the late reply, Theta Emerald was annoying to patch when it released in December 2016 but it should be fine now.
I'm on Android when I patch stuff, but I know how to patch stuff on PC.
There's LunarIPS and Xdelta for PC, and I can't remember off hand whether the patch for Theta Emerald was an xdelta file. If so, you'd want xdelta.
I have an Android app (ROMPatcher) that does all of that in one, but it should be just as easy.
Here's a quick guide:
https://nicoblog.org/guides/how-to-patch-games-with-pc-or-android/
I'm on Android when I patch stuff, but I know how to patch stuff on PC.
There's LunarIPS and Xdelta for PC, and I can't remember off hand whether the patch for Theta Emerald was an xdelta file. If so, you'd want xdelta.
I have an Android app (ROMPatcher) that does all of that in one, but it should be just as easy.
Here's a quick guide:
https://nicoblog.org/guides/how-to-patch-games-with-pc-or-android/