Question of a newbie

Hi all
I have few questions
1)how the youth academy player join in my team
2)after my club lvl up my players lost 1 star is it mean they lost their power too
3)what is the best way to win match without lost much energy.
Thx

1) when you go to your squad, you'll find 2 unsigned 18yo players. One 2* with 0T and the other one 4* for about 18T.
2)yes. You can see this in the player's skills section. You need to improve your players or buy other players.
3) don't use high press and man marking if you want to lose less condition.

Also I recommend reading as many tutorials as you can. You will learn a lot about the game from them.

yes, like this
Where are my players' stars? - Top Eleven be a Football Manager