How do I get past the "no root file system is defined" error?

How do I get past the "no root file system is defined" error?

I have a new computer with Win8 pre-installed and I wish to install Ubuntu
13.4 along side it. I have disabled Secure Boot and reset the BIOS to boot
from a live 13.4 stick. I have used Win8 to create an unallocated
partition on the hard drive. When I reach the stage of installing Ubuntu
where it says select the partition, I do so and get the error message that
"no root file system is defined," followed by "please correct this from
the partitioning menu." If by "partitioning menu" is meant the Win8 page
showing the partitions, I find nothing there that indicates how to format
this unallocated partition, or give it a "root file system," or label it
with letters like dev/sda, or speaks of a "mount" or notes where to put a
slash mark, or any of the other concepts I have seen mentioned in answers
to this question in your forum. If something else is meant by
"partitioning menu" I do not know where to find it. I would very much like
to join the open source community, but I am not an experienced IT person.
I need precise instructions that use recognizable terms (and not videos
with someone speaking with a thick foreign accent that I cannot follow). I
am not going to keep booting from a slow USB system, so if this problem
cannot be solved I will have to give up on Ubuntu. Hope you can help.