Just wanted to welcome you here Prushn! Don't worry, I was in your EXACT same situation only 4 months ago. I received SH4 for my birthday in December having never played a submarine sim before. There is much to learn, but that's a big part of the fun. Before you know it you'll be installing and tinkering with mods and making videos.
Welcome to the game and welcome to SUBSIM.COM!
Lance