ubuntu install do something else

i have a windows 10 z620
when i attempt to install ubuntu 18.04 it does not show the option of install along side windows 10.
My question is
if I choose to "do something else"
and in the unallocatted area of the hard drive I make 2 partitions
swap = 32 Gb ( i have 16 GB of ram ) and the remainder of unallocated I formate as ext4 root " "

then how does the boot grub loader "know" to offer a choice of boot?

In previous dual boot builds i get the option of install along side.
But I am not getting that this time

hibernate is off
did a powercfg /hibernate off
my win fs is clean
did a chkdsk /f C: ...and Yes it ran on next boot , ok
fast boot is disabled in bios

and when i (f9) to get to the boot menu I see that i am booting uefi to the dvd live disk , i have also tried a usb thumb ...same story

Thanks in advance