You need to set up XMMS2-Scrobbler's config files.
Config values that are specific to the AudioScrobbler server go in
	~/.config/xmms2/clients/xmms2-scrobbler/$SERVER_NAME/config.
You will usually have
	~/.config/xmms2/clients/xmms2-scrobbler/lastfm/config
and maybe
	~/.config/xmms2/clients/xmms2-scrobbler/librefm/config.

These server-specific config files contain your username and password
and the URL to use:
	mkdir ~/.config/xmms2/clients/xmms2-scrobbler/librefm/config
	echo -e "user: foo\npassword: bar\nhandshake_url: http://post.audioscrobbler.com\n" > \
	~/.config/xmms2/clients/xmms2-scrobbler/lastfm/config
For libre.fm, use
	handshake_url: http://turtle.libre.fm.

Optionally, if you're behind a proxy, you'll need to tell XMMS2-Scrobbler
about that proxy.  This information applies to all servers and so goes in
~/.config/xmms2/clients/xmms2-scrobbler/config:
	echo -e "proxy: my.proxynproxy_port: 8080\n" >> \
	~/.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 %%PREFIX%%/bin/xmms2-scrobbler to ~/.xmms2/startup.d/