Help Center

When your horse reaches 3 yrs old you can select which style of comps you want to specialise in: Classical or Western. You can change the style any time up till the horses 5th birthday (or anytime with the appropriate VIP perk).

You can then equip your horse with tack, and the competitions box will be displayed. The bottom centre comp will show a gold cup from Monday to Friday, which are the days the Grand Prix runs. Click on that box and follow the instructions from there.
Note, unless you have the appropriate HoP bonuses, your horse will need to have full energy and be at the start of it's day in order to enter, as Grand Prix comps use a lot of horse time and energy.