After you redeem the premium code you must manually download the expansions.
On PC when you double click the BF3 icon in your games library you should be prompted to download the expansions, if not right click the BF3 icon, select "show game details" and download each expansion from there. After they are all completely donwloaded start BF3, go to battlelog, then multiplayer, and at the top of the server browser page select the new maps and game modes in your server browser filter or you won't find any games on the new expansions.
On Xbox360
Redeem both the online pass and the Premium code and your Premium file downloads to your console make sure that you restart BF3 so the game initializes with the Premium file present. When you get to the main title screen you will receive a pop up stating you are now premium and you will have a Premium background. Next you will have to download the DLC expansions covered by Premium (the file just gives you access to download them but doesn't download them for you) via the Premium tab of the BF3 in game store (not via the Xbox Live Marketplace or it will charge you money again)then close BF3. After all 5 expansions completely download (this could take a while since each expansion is about 2 GB) start BF3. At the main menu you will receive a series of pop ups stating that you now have each expansion. Now from the main menu go to multiplayer, open server browser and then open the server browser filter by clicking R3 and check all new maps and game modes or you won't find any games on the new expansions.
On PS3
After you purchase Premium and redeem both the online pass and the Premium code and your Premium file downloads to your console make sure that you restart BF3 so the game initializes with the Premium file present. When you get to the main title screen you will receive a pop up stating you are now premium and you will have a Premium background. Next you will have to download the DLC expansions covered by Premium (the file just gives you access to download them but doesn't download them for you) via the Premium tab of the BF3 in game store or via the PSN Store then close BF3.
After the expansions are downloaded go to the games portion of the XMB and install each of the expansions by clicking on the bubbles. After each is installed start BF3, and you will get a popup for each of the expansion packs notifying you that you now have access to them. After that from the main screen go to multiplayer, then to server browser, and click R3 to open the server browser filter and check all new maps and game modes from the expansion packs or you won't find any games from the expansion packs. Now you are finished.