tried it and it wouldn't let me until I dropped someone else. Don't want to do that.

  

 That's correct, then u can put him on the DL and pick up another FA is you want.

  

A lot of this has to do with HOW the league was initially set-up (after the draft the setting cannot be changed) whether the option of player transactions is set for daily-today OR daily-tomorrow.

   If your league is set for daily-today, you HAVE to remember that if you place a player on the DL that day, you have to place him on the DL FIRST, THEN pick-up the FA....if your doing a waiver claim, the slot MUST be opened the DAY BEFORE so the waived player has a spot to occupy.

Daily-tomorrow is a tad more complicated, say you shuffle your lineup on Monday and notice one of your players is now DL eligible. You can DL him THAT DAY, but your roster will carry 1 LESS PLAYER that day. Any FA claim will be eligible to play on your team on Tuesday. Waivers work the same way as above but of course add the extra day.