Well, I would start
here and
here. Did you have a specific problem? It's rather hard to do a lot of (permanent) damage by installing a bootloader - I've never managed to do it. Just make sure you install to a drive (/dev/sda) not a partition (/dev/sda5) unless you know what you're doing. If it all goes wrong, then you can always re-install grub from a live CD
