Passwords? What are you taking about?
If you go into Jijimon's house and go on the computer behind him, you can input an eight digit password to get an email which contains some items. To find the email, go to your digivice, go to log then click on the email icon to view your emails. Click on the email you want to view and you will get your item(s).
Ok i just a password but it didn't work, what gives?
Well at the time of writing this only 4 passwords work and more will be added to that list every week. The 4 codes that work (perhaps more can be found on this page when you are reading this) can be found here along with more information:
http://buttzipper.tumblr.com/post/27485745080/password