Copy the @CBA directory into your Arma 2 game folder.
...\Arma 2\@CBA\addons\ => contains all the PBO files.
CBA should be added to your list of addons in the first position, so any other addons that depend on it can take advantage of it.
-mod=@CBA;@anothermod;@cheeseymod
CBA will automatically start its scripts and will automatically be used by addons or missions that require it, so there is no need to do anything more than this.