Dulfy has put together a guide to the beginning stage of the “Flame and Frost” Living Story, that is now active in the Diessa Plateau and Wayfarer Foothills maps: http://dulfy.net/2013/01/29/gw2-living-story-refuge-volunteer-events-guide/

How to Start the event

You don’t really start the event, you just go around in specific areas of Wayfarer Foothills and Diessa Plateau to repair roadsign posts, lit campfires, and loot mementos to handle to collectors (stars on your map). Each action give you 1 “act of assistance”. You will need 75 acts of assistance for the title and achievement. If you don’t see golden stars on your zone map, then your server is bugged and you will need to guest to a non-buggy server (i.e. Tarnished Coast) or switch to a different overflow.

If you’re looking for a guide for what to do, go check it out :). Dulfy also has lots of other guides/pieces of info about GW2, so you may also find other interesting nuggets of information on their site.