We agreed to play Heroes of Might and Magic III online! (July 2010 - December 2013)

I apologize for the question: but if I download champion templates, do I need to delete the default ones? Or how do I make the computer choose the champion template?

Install HD-Mod 2.98, for example; it contains all the popular templates, and you can simply choose the one you want. Plus, you can play in windowed mode, quickly split units, and transfer armies; it also has an auto-save feature.
http://sites.google.com/site/heroes3hd/rus/download