In the hills and fields above the town in White Orchard there is a herd of wild horses running free - among them are some gorgeous chestnuts, piebalds, and the odd black stallion.
So here is the thing - you have a horse - Roach - who you can call to you any time - and anywhere - you want him.... So you don't NEED to tame and capture a wild horse. This is not about NEED, it is about WANT. And you may WANT to have your own black stallion!
Taming a Wild Horse
You will notice that you can approach the wild horses and when you do, you will get the prompt to use the Action Button to mount them.
When you do that the wild horse will immediately buck you off, causing you to fall and do very minor damage to your buttocks. While the physical damage to you is next to nothing, the damage you can do to your armor is not next to nothing. So be aware of that as you climb up on to the horse you have chosen and get thrown off.
Are you tired of getting thrown off? Yeah? Okay so now we will explain how you actually tame that horse!
Open the fast menu (LB) and select the Axii Sign - the Sign that is used to influence the minds of your opponents. At this stage the horse that keeps bucking you off is certainly an opponent!
So, casting the Axii Sign will cause that wild horse to suddenly become all docile and friendly! Now you can climb up - and ride it - and it will not try to throw you off...
As long as you rode the horse while the Axii Sign was in effect, when it wears off the horse will be tamed and ride-able by you!
That means for as long as you like, in this region, you can ride that horse. No, it will not replace Roach. No it will NOT come to you when you whistle in the same manner that Roach does. No, it does not automatically receive the horse armor, blinders, bags, and the like and NO, it does NOT increase your max Inventory weight in any way!
What it does do is... Well.... Let you ride it. Yup, that is pretty much it. All that there is to it. Finola! Done!
But hey, Cowboy! At least you can say you mastered bronco busting (even if you DID have to use magic to do it)...