This should be very simple.
I downloaded the netinstall 64bit version from linux.org for my amd64 machine from http://cdimage.debian.org/debian-cd/8.5.0/amd64/bt-cd/
and downloaded the following image to my pc and copied it to my usb key., debian-8.5.0-amd64-netinst
I made sure that the bios read my usb key first.
When i boot, i see the machine briefly look at the usb, then it boots regularly.