It depends what kind of fansite you want to make! I'm not sure how to make a messageboards site, but the most popular is a blog! Two good websites to use are Blogger and WordPress, and it's not hard to set up an account and start blogging! If you're looking for some examples, take a look at the game's current fansites.
Hi! We are starting to get pretty full with the amount of official fan sites we can support; however, anyone may make a fan site for fun. If you're looking to be an official fan site, make sure you try to build a fan site that not only looks good, but one that fills a need in the community that no other fan site can provide. Follow the link that Pirates in the Sky provided and join in the fun!