Third Age Installation Help Thread

Ok so I'm downloading the Third Age mod for Medieval II: Total War. As of now, I'm downloading part one from this link: http://www.moddb.com/mods/third-age-total-war

After part one is completed, I am going to start downloading part two. For some reason, my connection is fine yet I've been downloading part one for about an hour and it's only around 50% completed. I suspect part two will take twice as long, forcing me to leave it overnight.
Nevertheless, I have a question: I downloaded Medieval II: Total War + Kingdoms expansion pack on Steam but I understand the Third Age mod installation  differs from a regular disc.

Can anybody give me a link or a step-by-step walkthrough on how to install the Third Age mod when I've downloaded Medieval II from Steam?

Many thanks.

PS: Sorry if it's in the wrong section.