making initrd to start a fresh installation

I want to know regarding the process of fresh installations when you
boot from a CD or DVD or from your hard disk or Lan for installing a
fresh copy of linux on your machine every vendor specifies kernel
image and initrd in boot directory on installation DVD or First CD
inside the installation ISO

/boot/i386/loader directory
initrd and a kernel image that gets loaded along with isolinux.bin
file and starts the installation
if I compile a new kernel and want to make an installable kernel image
and initrd from the vmlinuz and initrd of newly compiled kernel then
how to do that .
What I am not able to understand is how to make the bzimage and initrd
of newly compiled kernel which are in arch/i386/boot/bzImage
to be capable of booting for fresh installation that starts with a new
installation procedure rather than being able to boot with new kernel
with a few rpms that I already have from the ISO of my old
distribution
which are released when a new flavour of some linux distribution comes
with a new kernel.