Manager Guide: List Description
http://lists.uua.org/mailman/admin/listname/?VARHELP=general/info ("Details for info") allows you to write the introductory material for your lists's home page (http://lists.uua.org/mailman/listinfo/listname—everything above the link to the list's archives). Your list application included this information, so your initial text should already be posted.
Since this is the page that your would-be subscribers see first, it's a good space to give a general overview of your list's purpose. Be sure to spell out any acronyms in your list's name or your list's sponsoring organization. Include a link to your sponsoring organization's website, if appropriate.
After entering your text, click the "Submit Your Changes" button.