You could take an example from one of the other local communities, and set up a local community for Tunisia: http://www.linuxmint.com/communities.php
. Then spread the word online & offline and try to find other Linux Mint users in Tunisia. Linux users are generally easily found at universities in various studies.
Doing a Google search, I found that the Linux Professional Institute (LPI) has a local partner in Tunisia: http://www.lpi-maghreb.org/
. See also: http://www.lpi.org/blog/tunisia-small-c ... big-nation
. It could be worth contacting the LPI and finding out if they have knowledge of Linux user groups in your area, or if you can post a guest article on their website about the new Linux Mint community for Tunisia (once you have something to show