To "activate" a player from the DL, you must do it yourself.  Mainly, you need to drop an "active" player to make room for the incoming player on the DL.  Well, unless you have another player who is DL eligble that you can swap out.

It's good to be ready for Hamilton.  He's started playing in a minor league assignment and that's signifyes he's over the injury and ready to play everyday again.