If you have bought the modern shoutbox here at the plugin store (and i guess you did) you would not need to upload it. The easier way would be to click install package. Then type in the description field modern shoutbox. Or just shoutbox. Then hit ok. It will search for the plugin on the woltlab package server which is automatically added to the system when installing the wbb 4. Then you can easily click install and it will be added within seconds.. Good luck
Thanks mate all resolved now.