The Passwordcontroller collects all archive's (rar,zip,…) passwords. JDownloader is able to search this list for correct passwords while extracting. You can assign one or more passwords to each package. Often, JDownloader is able to fill the password filed automaticly.
To assign a password to a package you can
Doubleclick on a package and assign a password in the info panel. If you like to assign a password da various packages, select all of them→right click→edit password(s)
Just edit your global passwordlist at Configuration→Addons→JDUnrar →Passwordlist.