Materia Guide

http://www.ffxivinfo.com/materia/guide.php

This guide was pretty good source of information if you don't know anything about Materia in FFXIV:ARR. Once you've completed the level 19 story line quest "Life, Materia and Everything", you'll have quest markers for the 2 NPC's at the Bonfire that unlock materia melding and assimilating. They're just a single dialogue quest with a small exp bonus that unlock access.