First, get the player's club to accept your bid by either making a very high bid (many times his market value) that the club cannot reject or makingan inquiry and accepting the club's demands in return. When his club allows you to negotiate his contract, click to offer him a contract. While in the contract screen, click "News" on the left toolbar option (do not click the back arrow). Click on that player's name and withdraw your bid, then re-bid for free or whatever amount you wish. Click the back arrow on the left toolbar, this time back to the screen where you are discussing his contract details. Offer him a reasonable contract. When he accepts your contract, he will join your club on a free transfer (or the amount that you re-bid for).