Each owner in a keeper league is allowed to retain a small number of players they owned during the previous season, eliminating these players from the draft. All leagues are retained from year-to-year, regardless of Keeper setting. However, you are given the option to set Keeper rules for the upcoming season and the following year. If you decide you want to use Keepers this season, you can do so by opening the LM Tools page and then selecting "Yes" from the dropdown menu. You will be given options for how many Keeper slots to make available and when the keeper list locks. The same applies for the next season.
NOTE: If you are continuing a league from a different provider, you will need to select Keepers for use this season. You will then need to go into the Edit Team Rosters link and manually assign the Keepers to their appropriate teams BEFORE the draft. Also, if the League Manager allows draft pick trading, team owners cannot trade picks after keepers have been locked. So if you wish to trade draft picks, make sure you do so prior to the keeper selection deadline.