Life goal for an adult - I want to perform Vaulting on a Horse as much as possible at the Stables!
Here you need a 2-star horse to be able to perform vaulting. To unlock the 2-star horse you first have to complete the full collection for the horse trick hobby.
Go to the stables on the map and call your sim here with the whistle. Click on the 2-star horse and select the option Vaulting.