how to update game list

Hi,

I'm having troubles figuring out how to update your game list on steam. I just got Kane & Lynch 2 and would like to enter for dlc content but still says game missing. Forgive me if i've overlooked how to do it, but I just can't seem to find it. I've tried logging in and out of my profile in the upper right, to no avail. Is there any way to update? thanks for any and all info!