I got the Collector's edition for PS3 and thought "From Ashes" came with the 54MB online pass activation. Now it seems I need to add it and redeem a second code. I started my game already so I'm wondering if I download the add-on now will I need to start over to play it? Or will it show up during the game even though I've started?
Yes. You can install the DLC after starting a game and still access the content. After installing the "From Ashes" DLC, look for the mission called Priority: Eden Prime. The mission will be available to you in the game as soon as you board the Normandy and can use your Galaxy Map.