Make sure it will not go beyond the 4 primary partitions; if so then your PC will not boot up.
You can make extra partition with GParted--up to four primary partitions, or up to three primary partitions plus an extended partition that acts as a contained for logical partitions. This way you can effectively have more than four partitions.
Make sure you have sufficient space for Windows 8.
Install Windows 8.
Now you notice that only Windows 7 and 8 are listed in Windows's boot loader.
You have 2 option to make it so you can select Ubuntu when booting your machine:
Add Ubuntu in windows boot loader by using easyBCD.