Boot into the Live CD. Double click the Install icon. Go up to the point where it asks where to install. I don't know what to tell you if you haven't shrunk your partition yet, but if you have, choose guided install-use most continuous freed space. When you get to the next part with options, like setting up your name, there's gonna be an Advanced Options button towards the button above the next/cancel buttons. Click it. Make sure you check install bootloader. Leave the install area default. This will install the GRUB bootloader on your harddrive. It will automatically add your other operating systems to the bootloader. When your system starts up just choose what you want to boot into. You can configure the timeout [time before auto booting into default OS] and other stuff through Ubuntu. System>Administrator>bootloader I think.
That's all I remember off memory, but that will get your through it. Just remember to choose continuous freed space for the install and to click advanced settings when you see it.
