man lilo, man grub, google...
/sbin/lilo -b /dev/hda
(this will install lilo in the mbr of the master HD)
add an entry in /etc/lilo.conf:
image=/boot/<name of kernel>
run lilo again: /sbin/lilo
I don't use grub obviously but if you search here and/or google, you will find how to do this in grub