first I confuse about how to use it.
after try myself, then check the "support" here. and find also others coufuse about how to use it.
Finally I check the "Other Notes" tab, then it show how to setup it there.
Maybe should rename it into "Install" or just put the "other notes" page's contnet on the home page of the plugin
http://wordpress.org/extend/plugins/wordpress-mu-sitewide-tags/
