Your youth team coach will take care of the development of these players until you promote them to the full squad. At that point you take over
responsibility for their development. You control the pace and development of all your 1st squad players from the individual coaching
system.
In your weekly training schedule you can allocate sessions to individual training when the style of training is determined by the regimes you've set
from the individual training screen (bottom right). You can set each individual player to develop any of the range of skills or you can set individual groups
of players to a set skill ie you can set all strikers to finishing and so on.
This training will determine the direction in which players will develop.