I'm pretty sure that you just have to go to the 39 Clues website and register to start your own clue hunt. Hope that helps!
My agent card code is: P3GTRC9HX
The contest for free The 39 Clues cards expired in 2011. To get cards now, you must purchase them.
buy a book and go to 39 clues.com and make an account and then enter the codes on the cards!
Once you get the code, go on to the 39 clues website and create an account! After you do that that click MY CARDS and enter the code.
Rosemary You can not enter clues by the way. You have to do combos or missions.
P23HRFXFXP enter this to get the 6th clue
You can use them for the 39 clues tabletop game double cross. Also if you enter them on online, they are part of your card collection.
Play missions, go in arena 39, and enter card codes to get clues. Get all 39!! ~James the Janus Check out this reusable card code! P3GJW7JEXP
In the 39 clues site
P23HRFXFXP enter this in your cards to get your clue box
P23HRFXFXP enter this in your cards to get the 75th clue
Arctic.
enter the code P2C6DX6HXP