Press circle or B to bring up the MyGM menu, go to Front Office, then hit R2 or Right Trigger once and you'll see three options Player Finder, Propose Trade and Trade Finder. Select trade finder, then select the player you want to field offers for, when you're done, hit square or X and then you can see the teams who have offered you trades by using RB/R1 LB/L1.
Ok good deal, I thought maybe you could put someone up for trade and have offers come in randomly during the season.