Hello all, new to the forum

I used to have SH4 when it came out, but unfortunately was unable to play it properly at the time thanks to a machine that wasn't up to the task. I've recently repurchased it, and very much wanted the Narwhal mod to relive the days of playing Silent Service II. Having donated, I've downloaded the Narwhal Mod (1.8.5), but am completely stumped as to how to get it to work. Can someone please post a step-by step guide to doing this properly without me mucking everything up? I really want to get stuck into the game again, especially with my favourite US sub.
Much obliged!
Lambtron84