do you want to know how to install win 10 on a SSD off the USB?
You have win 10 a flash drive now? Has PC got or had win 10 on it before? Do you have a key if PC is new? If you have another drive in PC< it helps to remove it from power before installing win 10 on a new drive.
change boot order in BIOS so USB is first, hdd second
boot from installer
follow this guide:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
when you reach the screen asking for licence, if PC has had win 10 on it before, click "I don't have a key" and win 10 will continue to install and reactivate once finished. Otherwise enter key here if PC is new.
On the screen where you choose where to install win 10, if it gives you an error about GPT drives, delete all the partitions on the hdd and press next. If it still gives error, cancel out of the installer and restart PC and start installer again, it will accept next on that screen this time (some PC just need a restart here)