Thats why I said first read a tutorial on how to install Linux. Installing linux and windows are completely different.
Linux needs min 3 partitions
1. /- This the root, where you'll be installing all the files
2. /boot - This is where ur bootloader resides(Grub)
3. swap - Its like virtual memory
And there are many partitions u can create(depends on situatn and needs) but these 3 are primary.
Well.......Just delete the partition from Windows where u want to install Linux
Now boot with the Ubuntu CD/DVD(whatever u have) and while installing select "Install in free space" or sumthing like that. It will configure itself. Just review the partition before making any chages in next step otherwise u'll be left with nothing.....!!