Some of use are more likely using flash drives other than DVDs .

But mostly concerned with today’s topic
on How to make a bootable USB of windows Operating Systems
1 You Need A USB flash drive i prefer 8 GB depending on the OS size
2 Download /Buy Windows OS on any site you trust , for a free site downloads
  visit GetIntoPc
3 Download Rufus 
>Now run the Rufus software
>Under the Format Option on the right side of the software Interface
>Click the that disc icon and select you desirable OS
NOTE:If you have any valuable information on your flash drive make sure to perform a
backup . because this process will erase every single file on the Device and load up
installation files
>then let the process Begin by pressing the start button
It is a utility that helps format and create bootable USB flash drive , pendrive , memory stick
, USB drive etc
Here is the Video to help you out Practically :