Modding

Hello everyone! I've been looking everywhere, but I couldn't find the answer to my question. It's this: all mods for Heroes are installed in the UserMODs folder in the format "blah-blah-blah.h5u". So, how do I achieve this format for a mod? I unpacked the game's .pak archives with WinRAR, but I don't understand what to do next! Help me :smile45: