Windows 8 install from usb

[MKBeginner]

hey guys/ girls i need some help, what i want to do is install windows 8 from a usb drive onto a new computer i have finnished building, here is what ive done and got so far.

 

i have bought windows 8 from Microsoft online (download) no CD!

i have a 32GB USB drive with NTFS and bootable 

 

i have a setup.exe file from Microsoft when i finished my transaction. 

 

my new computer does not have a OS or anything installed on it already it is a 1TB WD black. 

Please help im so confused. 

[Thunderjolt]

Download this and use it to install the ISO to your USBStick

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDAQFjAA&url=http%3A%2F%2Fwww.microsoftstore.com%2Fstore%2Fmsusa%2Fhtml%2FpbPage.Help_Win7_usbdvd_dwnTool&ei=TM_NUsicMIiqhQfYy4DoAQ&usg=AFQjCNHAlqSq0Lq5i2VCo735KsCB0hIswA&sig2=SCqNAA5NTrcSgaGbVmeztw&bvm=bv.58187178,d.ZG4

[MKBeginner]

Says i need a iso file, where do i get that.