How to find the firefight option

This might be a silly question, but where do you find the Firefight Option in the game? I only have 4 Menu options to choose from. Campaign, Halo:REach Anniversary Multiplayer, Halo Waypoint and Extras. None of them lead me to the Firefight option. Thanks.

Go to the Halo Reach Anniversay Multiplayer section.

Then in Matchmaking, select Firefight.

Thanks