You can sort sponsors in the list by any of the columns by clicking on the heading Sponsors automatically adjust their requirements to meet a set quota of players. For example sponsor A's quota is to sign to 5% of the players, if they are below this then the sponsor will lower their requirements and conversely if they are above this quota they will raise their requirements. Sponsors can also change the amount they wish to offer as well.Sponsors can be signed at a set price for a fixed amount of days, ranging from 10 to 25 says. A sponsor may change it's requirements or price while you are signed with them however you will still remain signed with them until the contract expires. A contract with a sponsor may not be cancelled, you must follow the contract until the end.
You can see the list of sponsors you are currently signed to under the "Yours" tab, along with the duration remaining and the amount.
You can purchase extra sponsor slots, which allows you to sign extra sponsors. This can be found under the upgrades tab. The sponsor slot prices increase for every extra slot you purchase.