I don’t think this isn’t a terribly complicated or difficult feature to put together.
But I’ve had people ask me how I do it and decided I’d put a small tutorial together explaining it.
Here’s an example video of the sort of result you can expect:
Please keep in mind my tutorial doesn’t cover setting up the animations or controls for the horse itself or your character.
This tutorial is simply designed to get your character on the horse and put you in control of it.
You can find the tutorial here: https://wildwestdev.wordpress.com/2016/03/11/rideable-horse-tutorial/