Make sure to look at the solutions listed in [SOLUTIONS] UNAUTHORIZED DLC OR MISSING DLC @jonesey322. Also make sure that your base game is up-to-date (see patch 1.05)
If necessary there are two more threads that may help: POSSIBLE FIX FOR DLC NOT SHOWING UP IN GAME WITH ORIGIN INSTALLATION and HOW TO FIX SOME DLC ISSUES.
If you're still having trouble, give us as much details as possible (are you using Origin, Steam, your OS etc...) and the community will have a look.
