Really self explanatory on there. If you've not torrented before, pick up utorrent from here; http://www.utorrent.com/
, and install that first. You'll also need an unzipper to open the files. Windows 7 comes with one, but I've been using 7zip http://www.7-zip.org/
for years now (download the 9.20 .exe and run the installer) as well. Now that that is down, you can get on with downloading the mod.
When it's all downloaded (using utorrent, it will download the files automatically - it may take some time, but when it's complete, it will say under Status "Seeding". This essentially means you are helping to provide towards the download of the file for other people. You can stop this (right click on the torrent>stop) if you wish.
When it's downloaded fully, follow the instructions on the forum - namely resolving to the order in which you must run the .exe files, and then download and install the patches. The patches will install automatically.
To install the quick fixes, go to the location at which it's installed. I'm going to assume Windows 7, and because I have it installed on Steam, I shall go through that route -
Go to "Computer", then click Windows (C
/Program Files (x86)/Steam/SteamApps/common/Medieval II Total War/mods/Rage_of_Dark_Gods/data
This is the data folder, and where everything in the mod is contained.
The imperial campaign folder is found at this directory; data/world/maps/campaign/imperial_campaign - install the descr_stat quickfix here (installing means unzipping the .zip files in that directory - to unzip, assuming you're using 7zip, copy and paste the .zip file into the directory, right click on the .zip>7zip>Extract Here. To save space you can delete the original .zip file)
The projectile fix should be installed in the data folder.
The texture fix should be installed in data/unit_models
Go back to the Rage_of_Dark_Gods folder (not the data folder, the folder one level up) and install the data fix in that folder.
And finally, go back to the previously listed imperial_campaign folder, and install the final campaign script fix here.
It sounds like a lot of work, but it's really, really not. Rather than downloading every file at once, keep it easy on yourself and download each file as and when you need.