You receive two young players one 2* and the other either 3* or 4*. The two stars player you can sign him for free.

But the 3* and 4* player you will sign him for 12 tokens or 24 tokens it depends on the player's quality.

I recommend to sign the 2* player and sell him (if you are at higher level), but if you decide to sign the token player you should only sign him at the beginning of the season because as you advance to the next level all your players will drop one star.