Refer to Level 10 of this page: http://ffxiv.gamerescape.com/wiki/Gu...Locked_Content

You'll need to unlock the Guildhest section by doing on of the quests on your city of choice. (usually, home city)

As JimboTCB mentioned, you'll need to complete the guildhests one by one to get to the one you need.
There are two for each 5 level interval up to level 40. (i.e. Level 10 x2, Level 15, x2 and so on.)