Create ISO for Windows 10

Hi,

I am trying to upgrade to Windows 10.
I am going to install W10 on a new ssd.
I have downloaded the creation tool: http://ift.tt/1DcLU5q
I elected to download it to a USB drive.
I (mistakenly) thought I could just boot from the USB to load W10.

Now I need to start again.

I want to create an ISO on a DVD rather than use the USB.

How do I do this please, and will I have to download all the files again?

Thanks

Create ISO for Windows 10