To be clear a local community is something arranged and run by your local community (you and any other contributers), and once you have something in place and inform us your community will be added with your provided links and information to the local communities list on the Linux Mint website. A local community can be as expansive or as basic as you want. Browse around the other local communities to get a feeling for what they are doing. Some have not much more than a Facebook page, others have forum, blog and IRC all run in their native language, have a translated user guide, localized ISO images, and a translation team on Launchpad. Perhaps start a bit more basic till you can get other contributers involved
I'm not that web savvy, so perhaps somebody else can pitch in as to what would be easy, but for example you could start with a Facebook / Tumblr / Twitter / Google+ page for your local community where you share news from http://blog.linuxmint.com/
and discuss with other Linux Mint users in your language. You will probably want to reach out to other Linux communities that are available in your language to help spread the word and perhaps get contributers that are willing to help you build up the local community.