In the first build of the Early Access;
You start at the University, which is currently on a summer break. From there you can go and explore locations in Rein Ravine by the bus - after you've first found info about how to get there! At the Uni, you find interactable objects that contain important information, as well as clues to the upcoming storyline. Note, that you can inspect an objects more than once.
At one of the barns you can take a Riding Essentials course with senior coach Paola Giordiano, each lesson being around 15 minutes long (given that there's no fails). After you've learned the essential skills, you get a permission to start renting horses at the stable. The available rental horses and activities are slightly different every day. In the 'rent a horse' mode you can, for instance, test out the dressage mechanics - after completing the basic lessons, a book containing detailed instructions to the dressage commands, is opened. The Eventing Grounds area, containing cross country jumps, is also open to be explored in this mode. In the Flatwork Arena, you can make your own Flatwork exercises - up to 5 courses - and in the Jumping Arena, pre-made polework courses can be spawned into the arena. The equipment for spawning the courses are found in the corners of the riding arenas.
When interacting with objects as the main character (Ava), you need to use the right mouse button to focus on the objects first, then you can choose the interaction with the left mouse button. If there is more than one option, you can scroll through the options with the mouse wheel - or with E and Q keys.