If you are starting up a full community (eg, a localised copy), make sure you have the website translated, an irc channel, and a mailing list.
To create a mailing-list dedicated to the community speaking your language, you can send a mail to the administrator of the non-gnu mailing-lists at <sysadmin_at_gnu.org> explaining that you want a mailing list dedicated to gNewSense and which name should be gNewSense-users-** -where ** represents the two-letter language code as listed here.
After that
Announce on the main gNewSense mailing list, and in the #gnewsense IRC channel.