Glamours are unlocked at 50, from a quest in Mor Dhona "A Self-Improving Man". In order to use them you have to purchase from the market board or craft a glamour prism. Glamour prisms have different types (Goldsmith, Leatherworker, Weaver, etc) and different grades. To check which one you need click the gear you want to apply the glamour to, open the sub menu and select "Cast Glamour". This will bring up all the items you currently have in your inventory that can be used to glamour the armor you selected, as well as what type of glamour prism is needed. If you have the glamour prism then hit okay and it will cast the glamour.

Once applied the glamour can still be dyed if the item being projected is dyable. If you glamour an item that a job can not equip on to an armor that it can the glamour will not be shown, i.e. glamouring whm af onto a healer body then equipping it on sch.