Did you hear all about M O T H M A I L yet? If not, go here. If so, then I suspect you came here looking for more information about how to track down the special First Day Cover. I applaud your efforts and wish you to best of luck.
First, you'll need to find the launch location. We have an eye in the sky in the San Francisco area who will be posting updates about where the agent is hidden. Head over to Twitter and watch the feed of the @ElsewherePigeon He'll be updating more and more specific locations the closer we get to the evening of Saturday the 10th/morning of the 11th. I hope you and the @ElsewherePigeon are night owls...
Second, once you are at the location, you'll need to find our agent. You can read a description of her here. There may be others around who are also philatelically inclined. If you are stumped, they might help you out. Or they might conscript you to deliver their mail. Or they might make you fill out forms. Or all of the above.
Third, you'll need to provide the agent with a password. To uncover the password, you'll need to look into the research of Millicent DeWorde as @squeakinghinge on Twitter. Her work with The Paper has been of great interest of late.
Good luck and happy mailing.