Two/three questions

[Kaiser]

How do i get a sub job?

How do i unlock the moglocker/gardening section of the mog house

[Mhurron]

How do I use the search function in the upper right corner?

How do I use Google?

[Silent Howler]

There are two support job quests:

Elder Memories from Isacio, at (G-10) in Selbina
The Old Lady from Vera, at (G-10) in Mhaura

Both quests have a minimum level requirement of 18 to begin the quest. You only need to do one to be able to use a support job.

To obtain a mog locker you must complete Aht Urhgan mission 2: Immortal Sentries. However, in order to start this mission you must first gain access to Aht Urhgan. To gain access you Aht Urhgan you must obtain a boarding permit through the quest The Road to Aht Urhgan which coincidentally requires you to obtain the same items you need to find for both support job quests.

And as for gardening, all you need is a flowerpot and something to grow.