The digital extras, such as the soundtrack, maps and tactical guide, will be downloaded to your Steam installation directory for Arma 3, in the Bonus sub-folder.
example path:
\Steam\steamapps\common\Arma 3
This is the same for people who bought Arma 3 from Store.bistudio.com, directly on Steam, or selected Deluxe retail editions. Note: further tracks may be added to the soundtrack together with the campaign episodes.
If you have any further questions please use the form below.