To use XMMS2Scrobbler write your username and password to the config file
like this:

        printf "user: foo\npassword: bar" > \
                ~/.config/xmms2/clients/xmms2-scrobbler/config

~/.config is actually $XDG_CONFIG_HOME whose default value is ~/.config.

If you wish for XMMS2Scrobbler to start when you start xmms2d, make a
symbolic link from /usr/local/bin/xmms2-scrobbler to ~/.xmms2/startup.d/