Input Actions expose phases:

Example:

void OnEnable()
{
    jumpAction.action.performed += OnJump;
}

void OnDisable()
{
    jumpAction.action.performed -= OnJump;
}

private void OnJump(
    InputAction.CallbackContext context)
{
    Jump();
}

Read a value from the callback:

Vector2 movement =
    context.ReadValue<Vector2>();