How can I download the dlcs from the black ops 2 season pass from where I see it installed...

When you load up Black Ops 2 there should be an option to get the DLC from there. Downloading it from the marketplace will result in you being charged again. If you don't see an option to get the DLC when you load up Black Ops 2, find the season pass in
the marketplace again, it should say "download again" instead of listing the price, once it finishes, try loading Black Ops 2 again and see if it fixes it.

If he entered the code correctly then he should have the season pass. To make sure it's downloaded go to My Games and Apps and hit the start button (black button with 3 gray lines) on Black ops 3. Then go to Manage Game. From there you should see the season
pass and dlc. If you click on the season pass, it should prompt you to install if you haven't. You should also be able to install the maps from the main menu after you load up the game.

If you don't see the season pass you can search for it in the marketplace and try to download it there.

Yes, they give you points to download the season pass, not the actual pass itself. You will need to navigate to the marketplace and download the season pass from the Black Ops 2 sections. Alternatively, you can download the season pass from the in-game menu
for Black Ops. Once you download the pass, you will have to download the individual content as well, except now it will show up as free.

Q - If I buy a Season Pass, will I get early access to the Call of Duty®: Black Ops 2 DLC Map Packs?

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A - No, fans who purchase the Season Pass will have access to each of the Call of Duty®: Black Ops 2 DLC Map Packs on the same date as those who purchase the DLC Map Packs á la carte for their respective platform.

From the link in the first post.

Hi RiskierToast 553!

Is it impossible for you to manage to piece together the codes from the shredded Season Pass?

Unfortunately, Activision has recently announced that they won't be providing new Season Pass codes for players that reported their missing or lost.

www.examiner.com/.../activision-comments-on-missing-call-of-duty-black-ops-2-season-pass-dlc-codes