How to download free DLC from Steam

I have looked all over, and unless it is included automatically, I can't find the free DLC that was released for Napoleon. Also does Steam automatically update the game when patches are released?

This is my first Total War game that I don't own on disc, so I'm not used to using it with Steam.

Thanks!

steam automatic updates by default, you can change it by right clicking the game and then going to properties.

It downloads everything automaticly including the ones you have to pay for so your computer knows what its doing if the enemy uses it in mp. Its only unlocked once you pay, the free ones are already there, check if you have the free units.