I'll take a stab at it
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Open up "Musicmatch Jukebox", then at the top left of the window click on "File", then in the drop down menu click "Watchfolders". Another window should open, check the box "Enable Watch Folders"(if it isn't already), then click "Add", find your "shared folder"(the default is C:\Documents and Settings\"your account name"\Shared), hi-lite it, then click "ok" and if all goes well that should be it. Everytime you open Musicmatch it should automatically add any new songs.