Players can move from one team to another through the game's transfer market. You can either sell or buy a player from another team, or loan a player in or out. Loans and transfers work based on a bidding system which is explained below.
Buying or Loaning In A Player
You can access the Transfer Market via the Transfer menu. There you can see all the players listed for loan or for sale by other teams in the game. There are also teamless players who do not play for any clubs currently.
Once you decide on a player to buy, you can click on the player's link to bring up the player details page. From there you can place a bid on the player. The minimum amount you can bid is the player's asking price (or value if he is teamless), or 5% above the current highest bid if there are bids already placed on him. If your bid stands until the deadline without anyone else bidding an amount higher than you, then the player will join your team. The deadline is set as 12 hours from the time of the first bid, and each new bid will extend it to 8 hours from the time of the most recent bid.
For loaning players, you have to pay a signing fee, and the player will join the club offering the highest signing fee among all bidding clubs. The minimum signing fee you can offer is 2% of the player's value, or 5% above the current highest bid. However your board might place restrictions on the maximum amount you can bid based on the available balance in your bank.
Keep in mind that you cannot withdraw a bid if it is currently the highest bid on a player. This applies to both purchase bids and loan bids.
Buying Teamless Players
Players who do not have a team currently can be purchased immediately without going through the bidding process as in the case of other players. Teamless players can be found under the "Teamless" tab on the Transfer Market page. The purchase price of teamless players will be 80% of their value.
Listing A Player In The Transfer Market
You can put a player for loan or for sale in the transfer market via the player details page. You need to set a minimum amount that you are willing to sell the player for, which should be atleast 40% of the player value (20% if the player has announced his retirement). Any teams who wishes to meet that price can then bid on the player from the transfer market. You can always withdraw a player from the transfer list until somebody decides to bid on him.
You cannot list a retiring player for sale, or place a purchase bid on a retiring player after one-thirds of the season is complete. Similarly, listing players for loan and placing loan bids will not be allowed by the system after one-thirds of the season is over. However the bidding process will continue as usual for retiring players or players listed for loan if there were bids placed on them before this deadline. All retiring players and players listed for loan will be automatically removed from the transfer market after one-thirds of the season if there are no pending bids on that player.
Also note that players cannot be loaned out to another club after they have announced their retirement.
Transfer Market Restrictions
You can buy or sell as many players as you wish given that you maintain your minimum squad size limit of 18 players and the maximum squad size limit of 30 players. You can also loan out 2 players from your team per season to help them gain experience, and loan in 2 players per season, as long as the above mentioned squad limits are maintained. The current status can be viewed from My Transfers link under the Transfer menu.
To ensure fair play, you are only allowed to buy one player from the same team in a season. Similarly, only one loan deal (in or out) is allowed between two teams in the same season. This means if you loan out your player to another team, you cannot loan back a player in from that same team that season.
A transfer ban for 14 days will be placed on a player once he completes a transfer from one team to another. He cannot be listed for sale on the transfer market during this period, but he can be loaned out to another club. All players on loan will return to their own club at the end of a season automatically. However you can always send back a player from loan after two-thirds of the season.
Sometimes, you might have a player that is not in your team's plans at all, and might be hard to sell in the transfer market due to his age or low attributes. If you feel that it is not worth it to keep that player in your squad, you can release the player from the player details page. You will be paid 30% of the player's value upon releasing him (10% if the player has announced his retirement).
Players who have decided to retire at the end of the season cannot be released from the club after one-thirds of the season.