How to summon your chocobo to a fight?

It's been a while, good day everyone.

I have to open another of my nooby-question topics. I swear I tried to find in the forum a thread about this, searching for companion tag, but after a hour searching and don't finding anything useful I suppose it is time to open a topic and hope to some nice person to answer the doubt.

And here it comes, I obtained the chocobo with my first character and also this newest one, but.... I still don't knowing how to summon it to fights for making it level up and all that. All I know is that I need the gysahl green thingy.

When I open in characters -> companions and click in summon, even having the gysahl thingy, it says something like "You don't have any companion" or such, can't remember.

An experienced player of the server told me that I needed to use some quest for that and to google it.... Uhm.... May you know which quest?

Thanks in advance ^^

First you need to get to level 30. That's when the companion quest unlocks.
The quest itself is in Camp Tranquil in South Shroud. I don't remember the name of it though.

"My Feisty Little Chocobo" is the name of the quest

And once you've completed the quest, you'll have a 'Companion' tab added to your main menu. You can then drag the Gysahl Green icon to any of your hotbars and just clic that whenever you want to summon the feisty menace to your side.

Also, here's a bit of advice when levelling your chocobo. Pick one of the trees and stick with it if you care about achievements. There's a different one for unlocking the level 10 ability for each role. Although a chocobo that has points in all 3 trees will be stronger, you'll me missing out on the achievement. They may or may not add an item at some later date that will let us reset a chocobo to level 1 so we can earn all 3 achievements.

And don't feel bad about posting your questions here, that's what these boards are for.

Thanks everyone for the help, I obtained even more information that what I thought I would. I'll use it wisely ^^