Where should new maps be placed?

In the file explorer, navigate to the folder where the game is installed (if it's the 1C edition, the default location is C:\Program Files\Nival Interactive\Heroes of Might and Magic V: Tribes of the East; for Buka, it's something like C:\Program Files\Buka\Герои Меча и Магии 5:Повелители Орды, as far as I remember). Then, find the Maps folder, go into it, and copy the maps there.