I don't mean to hijack your community guide, but you could also point everyone to this article:
https://blackdesert.zendesk.com/hc/en-us/articles/115003929669-How-to-claim-DLC-for-STEAM-users

1. My BDO account is the one i Bought from Steam
2. I've just purchased Bronze to Silver Package Through Steam
3. In the game I have press F9(community) --> 1 (Redeem) . and Redeemed the Package
4. I then check my in-game Mail . And Click on the mail titled "Web Storage" as well as the item inside the mail
5. Then i went to https://www.sea.playblackdesert.com/MyPage/WebItemStorage by logging in via STEAM
6. There is nothing in the Web Storage
7. There is also Nothing in-game. no peguin . no horse. no pearl . nothing.

Any idea?

This guide is old.. doesn't help

hey I know this is an old thread, but I just started playing, and I'm trying to claim a code from the GM but when I clicked redeem button on the new UI, it takes me to the last picture. So where do I I input the code that I got?
thank you

ty helped alot

i will add final step
> after claim your steam dlc by click use, open your mail [esc > notice > receive]