Understanding Free Agents
This article explains how players who are unowned are free agents, and also covers how to edit your roster by adding or dropping a player.
All unowned players who have cleared Standard waivers are free agents and are available on a first-come, first-served basis. All claimed players would immediately be added to your bench for the following day's games. It is then up to you to move them to starting positions.
You can pick up or drop a player by clicking on the Add or Drop links located near the top of your Team Page. You also can click on the Players tab to see the available Player List.
You can drop players without replacing them, but you can only pick up players without dropping someone from your roster if you have less than the maximum number of players on your roster. You will never be allowed to exceed your league's roster limit.
Before the start of the season, all undrafted players will be placed on waivers, with those left unclaimed then being treated as free agents. You can find out the length of the waiver period for your league by clicking on Scoring & Settings from your league homepage.
In Public Leagues, you are free to add/drop as many players as you like during the season, but you should check your league settings in a Custom League to see if the Commissioner has established a transaction limit for your league.
Once your league has drafted, you can keep tabs on prospective players to add to your team by adding them to your Watch List by clicking on the flag in the Action column:
You can have up to 50 players on your Watch List, which is accessible by clicking My Watch List on your team page.