This is where you learn how to play.

Start here:
https://community.sigames.com/topic/295001-how-to-play-fm-a-twelve-step-guide/
http://www.guidetofootballmanager.com/

Pairs and Combinations:
https://www.passion4fm.com/football-manager-player-role-combinations-duty-pairs/

Tactics:
http://community.sigames.com/showthread.php/377489-Creating-A-Tactic-Design-Create-and-Maintain

Team Shape:
https://community.sigames.com/topic/401273-what-is-team-shape/

Team talks:
https://strikerless.com/2016/02/19/the-hartman-doctrine-why-the-hairdryer-treatment-works-surprisingly-well/

Scouting Guide:
https://fmcoffeehouse.wordpress.com/2015/04/24/creating-a-scouting-system-in-football-manager/