I would venture that the red +ve would go on the bolt head that fixes the battery cable to the starter motor, the black -ve where the earth strap is
![[Linked Image]](https://www.tm-img.com/images/2020/06/20/20200620_180510.md.jpg)
Now the observant will see that in this photo there is an extra cable on my car because I have fitted an Anderson connector to the inner wing for easy jump starting
![[Linked Image]](https://www.tm-img.com/images/2020/06/20/20200620_180530.md.jpg)