Bought Skyrim, Dawnguard and Hearthfire from Steam store; can I install Dragonborn from Legendary CD?

[Sleevee]

I was given the Legendary CD as a gift, and I'd like to install Dragonborn from it. Reinstalling from the disk hasn't worked. Can I do this without completely uninstalling and reinstalling?

[Sibyl]

if you have the game files and put them into the skyrim directory when you begin the download it begins preparing it will find the game files and use them.

[Rhuto]

Since you own the game, Steam don't instal from disk.
What you must do is to put the disk key into "Games" Activate a product in Steam" then you will have it all.