- Run your Battlefield 4 game and then go to the Home Screen.
- Go to Add Ons (usually appears on the right of your main Home Tile or you can go to Store) and search for it in All Add Ons.
- Find the Second Assault DLC and open it. Instead of a price you shall see an option to Install.
- Do the same with China Rising. If you're loading both at the same time then the 2nd download will say Queued and will start automatically.
If you want to play something else then it will download in the background but may take longer to download because you're splitting your consoles resources. Once you've done this then you now have access to Second Assault and China Rising. You'll no longer get confusing messages telling you that the content isn't there even though you're a Premium Member.
Hopefully that's helpful to some people.