WCIII Install help needed

I have the .iso image data for WCIII extracted to my DOS folder in four subfolders aptly entitled, Disk1, through Disk4, but now I'm at a loss as to how to use this data to install the game using DosBox.
I've used DosBox for ages but never in this application and finding a video tutorial that matches this situation has been like finding the proverbial needle in a haystack..
The only tutorials I have found online so far are for imgmounting a single .iso image on a physical CD and not what to do in the event you've extracted the data to your HD.
Any technical knowledge or direction to a tutorial in this regard would be greatly appreciated.