How to transfer players from my U-23 squad?

I am playing as Seattle in MLS and there are a few players that I want from my U-23 team. When I go to sign, it says that I can only sign domestic youth players once drafted. That makes sense, but I thought I had exclusive rights to my U-23 team. And if not, how will I know when they go into the draft? When will they go into the draft?

Thanks in advance!!