My boyfriend was young & didn't really know what he was sighning. Now the mother of his child has all rights and uses this to hold the child from him. Is there any way to get his rights back? Or some sort of visitation arrangement the courts can make?

It is rare that any court would have taken away his rights, just signing something, that was not approved by the court means nothing.

He can get visitation by filing for it in court. ( what he needed to do, long time ago

Typically, a father in a situation like this may not contest a court action by the mother for sole physical and legal custody. That is different than "signing away parental rights", and I suspect that this is what may have happened. If at the time he doesn't ask for a specific visitation schedule, the court is not going to go to the trouble to force one on him. It would be reasonable to now go back to court and request specific visitation.

Was this done through a court? If not then he can go file for visitation.