Note that some pieces of content need to be downloaded to be available in game. If there is no price tag, you can safely select it and download it. In the other case, you'll have to purchase the content before being able to find it in game.
Moreover, some content may need to be further unlocked through gameplay: certain missions, for example can be selected in the DedSec app only after a certain amount of followers is reached.
If you own the content but can't find it in-game, it may be that you need to play further to unlock it.