Installing GRUB on second disk

I've managed to install FreeBSD on a partition alongside Windows but unfortunately I can't get either to load up. I thought I'd try and install GRUB on the disk by booting FreeBSD of second disk. The proble is I'm not sure how to install it... I can run grub-install /dev/ada0
but how will GRUB find it's config files? I'm currently (temporarily) booting from /dev/ada1 and FreeBSD is installed on the second partition of /dev/ada0.