The option for FCFS waivers is only available in private leagues and must be activated by the commissioner. Commissioners will see this option available while creating the league.
FCFS does not completely get rid of the FAAB element of waivers; it is an addition to the Wednesday FAAB waiver run.
Following each Wednesday's 3:00 PM ET blind bidding period (the only bidding period of the week if FCFS is enabled), all remaining available free agents can be added on an FCFS basis up until a player's respective kick-off time for that week. FCFS opens at 7:00 PM ET.
Once an available player's game kicks off, the player is locked until the next week's blind bidding period (on Wednesday). FCFS transactions are free, so even those with a $0 FAAB budget can still make FCFS transactions.
Players dropped during FCFS are eligible to be acquired in the same week if the setting is enabled by the commissioner.