respected person

I have an laptop hp pavilion g6-2312 ax,runs windows 8.1(uefi boot loader)
actually wanted to install ubuntu along with windows 8.1 and came to know that ubuntu runs on mbr and don't have that type of partition table on my pc I had even tried to load ubuntu on external hard drive but does not loads at all after installation
it doesn't show that there is any operating system already on the hard drive to install it along win 8.1

if i try to install grub, it doesn't load windows 8.1 ....please help me so that it can be useful