if you want this model to replace captain fully just do the things below
when installing go to where you have installed you're warcraft 3 and then put it inside (_retail_\units\human)
and if some of the texture specially the shield texture don't work
try to change it's path by putting (units\human\thecaptain) through the retera model studio in tools\edit textures

2nd replacable textures are the icons of the captain just put it inside _retail_and you should be good to go with the icons

this model was made possible by (Burned Smackdown) what i mostly did was just change a few things starting from his helmet in his portraits and also his portrait camera should be changed i tiny bit oh and disclaimer this is only a derivative

you can get the icons from the link below (just press model)
Link to BurnedSmackdown's model