Where do I install Windows 8?

Hi, I am trying to perform a custom install (clean install) of Windows 8 onto my computer. Entering the product key is all done but now it's asking me where I want to install Windows. It gives me two partitions to choose from but they both display this error: 'Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be...