Tutorial and beginner guides
For new players to HOI2 and its variants (Arsenal of Democracy and Darkest Hour) below are some links and some YouTube videos to help beginners.
Check out the The Bunker's wiki page for FAQ and Strategies
An AAR article:
https://www.hoi2bunker.com/post/how-the-heck-do-you-play-this-game-a-simple-tutorial-aar
YouTube Videos: