how works the mod in arma3?

[teoleo 2]

How i install it ( like arma 2?) and how i active and de-active it?

[chortles 263]

Almost exactly the same ways as with Arma 2. :) You still create a modfolder for it (i.e. @themod) in a Arma 3 directory (either the game directory in your Steamapps\common directory or the profile directory in My Documents), and you enable or disable it through Configure -> Expansions in the game.

[CyclonicTuna 87]

I'd recommend PlayWithSix: http://play.withsix.com/

or Arma 3 Sync: http://www.armaholic.com/page.php?id=22199

to accomodate your mods once you've made a modfolder to store your @modfolders. This makes it much easier to launch Arma with or without the mods you want, and keeps everything in order.