How do I install Ubuntu on a seprate partition on a laptop running Windows 8 on another partition?

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http://askubuntu.com – I have an Alienware M14x R2 with W8 64-bit running on it. I had created a seprated partition (150GB) and Linux-swap (1GB) using GParted, before I installed W8. Now I want to install Ubuntu 12.10 on this partition. How do I do that. When i ran the USB (with ISO for Ubuntu on it), I could Install Ubuntu, but it is not on the 150Gb partition I created. Help appreciated. Thanks Ranveer (HowTos)