How to change what buildings build/change the texts and Icons they have:?

[Jakass]

Hi,im a noob editor(Only knows how import unit models and stick them on another model)ı have a problem.I downloaded some another footman ımage and added it onto a footman and called it guardian.I have an ıcon for it but i dont know how to dismiss footman ıcon and place my icon.(barracks)

2nd problem:I want to enable producing buildings to build/Produce something else from what they already produce(For an example ı want to produce a dragonhawk from barracks)

Can you help me and be specific plz.

 

[Pharaoh_]

Go to the footman unit and check the field Art - Icon, then from the new window, the field "Imported" and select the custom icon to set your new one.
Go to the building unit, and Techtree - Units trained

 

[krisserz]

And don`t add prefixes.