If it is rolling to the left, push the right trim button a few times; if it is pitching back, push the forward trim buttom a few times. That looks like a really cheap quad, so chances are those buttons might not even be wired to anything lol
Even simpler solution is to tape pennies in the opposite side that it is drifting to help balance it out. Ultimately, something like that will never hover perfectly in place because it does not have any velocity sensing--just IMU attitude estimate--and will require pilot input to keep stationary