Tails:
Open your AH2 Folder. Inside, among others, you will see a folder called Sounds. Delete it. Now paste your new Sounds folder (the one you just downloaded and unzipped) into your AH2 folder. Your just replacing one Sounds folder for another. If you ever want to go back to default sounds, just delete the new Sounds folder you pasted in there. The next time you play the game, it would automatically put a new default Sounds folder back in.
Long story short, adding a soundpack is simply replacing one Sounds folder for another. Any probs, just PM me.