Thanks, guys.
Sorry for being so annoying lol.
I just figured that I could sort of teach myself another way - in the middle of a game, pause and go to coaching/strategy, then go to defensive formation (or offensive formation) and cycle through each play. It teaches me where each player plays, so I can make a good decision on who to mark up with.
I am currently playing Franchise Mode with my created Eels team, and I chose, instead of drafting NFL players, I would do the fantasy draft - I chose to have a defensive team. As a result, all my defensive team is 28 or under and they are all at least 80 overall - meaning my defence is 93.
Problem is that sometimes my DT, because he's 5'8 and 210 lbs, gets pancake - and they get no pressure from the defensive line and so the QB throws a mad 1 million yard TD pass lol.
And I can't substitute him - he's 93 overall, 85 for strength and 90 for running blocks.