Waive goodbye to the players you don't want
Now that you've probably drafted one too many players, out of which you will end up using only a few, it's time to use the old ones to something useful which will help you improve your current roster.
Basically you can waive the players you don't want and send them away so that you can get some Player Points. Once you have some players let's say C Tier players or B, or even A Tier players which you don't want or will never use, head on to the My Team tab, and there you will see the Roster tab.
Select the Fast Waive option in the bottom side of the screen and then select which tier players you want to get rid of. That will automatically send them away and give you in return Player Points which you can spend in the Player Exchange shop.