Castle Maelskull (HAR HAR HEMAN) is at 1400 65 900.
My Chocobo Ranch is right there too.
If you go inside, there are lockers with everything you need to get started.
ALL Chocobos outside (in the fenced area) with NO collars (red) are free. There are yellows, greens, blues, whites, and blacks. Please do not mess with the birds in the pens, and do not open or close pen doors (they are the way they are for a reason)
You want a stack of Gysahl Greens, a Chocopedia, a Chocobo Saddle, and a Chocobo Saddle Bag.
Go find the bird you want (The blacks are the best free birds out there, but if you want to start out with a lesser bird to learn on, get a green (climber) or blue (water treader). Whites and Blacks are basically the same, but Blacks give night vision while riding them.
Right click them with Gysahl greens until you see hearts and a collar appear, it is now your bird. Do NOT tame birds and leave them, if you tame a bird, take it to your house (unless you are just parking it while you are visiting it).
Once it is tamed, put a saddle on it. Now put the saddle bags on it.
Now put the Chocopedia in your hand and right click the bird, it will bring up a menu allowing you to make them follow, stay, change their name, or drop their gear. Dropping gear gives you back the saddle and bags (if any are on it).
Put something else in your hand, right click, and ride away. Most Chocobos can jump over the double doors on the west side of the ranch. The Whites and Blacks can both (I think) jump over the fence too.
If not, go to the double doors, dismount, open, remount and exit, dismount and close the doors behind you so the rest of the birds don't get out.
Keep Gysahl greens in your toolbar so you can heal your bird if it gets hurt (you can right click it with a green while riding it to heal it)
You can also set up an area with straw and a cauldron of water... park a bird there and it will heal itself.
If you don't have a chocopedia on hand, you can right click the bird with a choco feather to make it stay or follow.
Non-Gold/Purple Chocobos will take falling damage... be careful with them! Heal them any time they are hurt.
Chocobos following is pretty bugged, stay out of low tree areas and super high hills (best bet is to just ride them, not have them follow you).
Look up the Hexxit wiki if you want to breed them yourself.