USB boot disc

I'm trying to make an EasyRE recovery USB to fix a computer that's running Windows 7.
So far I've installed downloaded both EasyRE and Easy BCD onto a different computer running Windows 8 and followed the instruction as shown on the site all the way down to Step 6: Change the name and type (on Use EasyBCD to create a bootable USB section).
The textboxes and buttons in the ISO tab are all greyed out so I'm unable to select or click anything there.
My attempt to look for answers on google was to no avail.
Any help will be much appreciated.