Not sure of your reason for changing bootloaders, but to use LILO (assuming you have it installed) all you need to do is edit the file:
/etc/lilo.conf
and type the command:
lilo
(do this as root).
Try the How-To's at
www.linuxdoc.org for LILO specific options.
You may be able to find linuxconf easier to use to change the boot settings.