[FraserOliver17]

Your youth team, think of it as a heavily watered down FM style. with players added when players in the system become too old, or to fill gaps from payers you've promoted. As I understand (because I decided to re do my ML when all the tactics are done - FML) CPU teams will end up with new players occasionally as well through regenerated retirees in the game being spread out across the teams. You can of course continue scouting throughout the seasons and find young players, but if you sign them they will go into the main team and not into the youth squad, so you will need to get them minutes where possible.
Of course, this is just how it's been previous years. I haven't finished my first ML season yet so I may be way off base and stand to be corrected