Click on the dropbox icon on the top of your screen, hit preferences and tick the button where it says Start dropbox on system startup in the general tab.
Run the command in this way: ($HOME/.dropbox-dist/dropboxd &)& this will detach the process from tha actual terminal and put it in real background.
To reset Dropbox prior to reconfiguring it, or to prevent it popping up every time you log in, use the local command reset-dropbox which kills all dropbox ...