you need to get the quest from the GC Officer.. not the one that signed you up and not the quartermaster.. not exactly sure of the npc's title but should be the one standing off to the side from the other two.. once you talk to him and get the My Little Chocobo quest, then you go to the GC Quartermaster, in the first Rank selection box (private/corporal ranks) and look in the Materials tab for the chocobo issuance for 2000 seals, you take that to the chocobokeeper of your town, they will bring out the chocobo for you, then you have to talk to the chocobo and give it a name, then talk to the chocobokeeper again to complete the quest and get both your mount and the license to unlock all other mounts as well.