Call of Duty Modern Warfare ltiplayer can't get in?

I play Call of Duty Modern Warfare on my Xbox one but whenever I want to start the game warzone it says I have to update to play mw how does this update work?

An update?

I just don't know if I really have to download everything to play multiplayer

Special unit followed by a campaign and so on

No, if you want to play the multiplayer you only need the data from the multiplayer the same applies to campaign, warzone and special unit

And how do I get this data?

If you press multiplayer then something should come up like you are missing game installations or packages