How to play the campaigns in the standard version of Heroes of Might and Magic V, specifically the Tribes of the East expansion.

Google a mod that unlocks the original campaigns and the Lords of the Stronghold in Tribes of the East.

Great, and thank you very much for telling me to Google it!!!
I'm waiting for a proper answer, because I've already Googled it, but it didn't give me any results; I tried different search terms.
If anyone knows how to do this, please write.