how and where to change the default font and theme of Ubuntu 11.10 ?

[Sharl.Jimh.Tsin]

hello,everyone:
	i upgrade to 11.10 from 11.04 last week via dist-upgrade,and i found
that i can not change the font of the system,actually i do not find the
place to do this.

i check the "Display" panel,there is not relates settings.

and i also have no idea to change the theme of system,i installed some
3rd theme via "Ubuntu Tweak" tool,but they does not appear in the theme
list.

that's all.Can someone help? thanks~

-- 
Best regards,
Sharl.Jimh.Tsin (From China **Obviously Taiwan INCLUDED**)

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