download the
Windows 10 media creation tool and use it to make a win 10 installer on USB if you don't have it now
what do you want to do with data on hdd? leave as is or wipe drive?
1. unplug PC, unplug hdd and install ssd so its only drive plugged in
2. change boot order in bios so USB 1st, ssd 2nd unless there is an option to boot from USB on 1 boot and then set ssd as main boot (some motherboairds allow a 1 time boot choice)
3. boot from installer
4. follow this guide:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
when you reach the screen asking for licence, click "I don't have a key" and win 10 will continue to install and reactivate once finished
5. Boot from ssd a few times to make sure it works ok.
6. unplug PC, attach hdd to power again and boot up. look in bios to make sure hdd isn't added to boot drive list.
if you want to keep hdd as is, you can do that. You can delete the old windows folder on drive but it will still leave the old boot partition on drive so if for some reason later on, the ssd doesn't boot, the PC might choose the old boot partition but it won't load windows if the folder is deleted.
You could copy anything off drive and wipe it later on if you want.
To wipe drive, go to settings/update & security/recovery
under advanced startup, choose restart now button
this loads you into a blue menu at startup
choose troubleshoot
choose advanced
choose command prompt
type
diskpart and press enter
type
list disk and press enter
this shows all drives available, DVD/USB and hdd, make note of hdd number
type
Select disk X - where X is the number of the hdd you want to wipe, change X to that number and press enter
once the drive you want to wipe is chosen, type
Clean
restart PC and then use disk management to partition and format hdd so you can use with windows.