Press B to bring out your Stand, T to call your horse after falling off, and F for the one-time boost. These controls come from the official game description for A Bizarre Run by Current.

PC controls
Keyboard reference from the official game description. This is not an in-game menu.
Pressing C and holding C serve different purposes. If you want a different secondary item, use the selection input first. The official description calls F a one-time boost but does not specify when it resets, so avoid treating it as a repeatable sprint button.
For Stand abilities and inputs on mobile or controller, follow the prompts shown in your game. The table above is a keyboard reference.
From the tutorial to registration
The community walkthrough describes an early-access sequence of a random Stand draw, a practice race, combat exercises and a tutorial boss before the lobby. Its exact launch-version menus and triggers remain unconfirmed.
Use those as progress checks: have you finished the riding lesson, completed the combat prompts and reached the lobby? If you are still in the tutorial, finish the objective displayed there before looking for race registration. Once you reach the lobby, look for registration rather than assuming every activity starts a race; the official game also has a separate Battlegrounds mode.
Before using a Stand item, decide whether you want to keep your current Stand. The reported slot system makes that choice important; check Stand slots and replacement before consuming anything.
When you get stuck
| Situation | What to check |
|---|---|
| You fell off your horse | T is the official horse-call input. |
| You want your Stand | Use B for this Current. version. |
| You need a different secondary item | Hold C to choose; pressing C takes out the selected item. |
| You do not know which combat move to use | Read your equipped Stand's displayed prompts. |
| You reached a barrier during the race | Check whether the screen shows a timer or Deaths Needed; see the Stage 2 checkpoint guide. |
For your first race, learn where each stage sends you before experimenting with unfamiliar routes. Keep the Stage 1 and Stage 2 objectives nearby for the reported sequence after registration.