its easy actually. just go to this site and get a usb drive (at least 8Gb). the tool will guide you pretty straight forward.
https://www.microsoft.com/en-in/software-download/windows10
when booting your computer to USB, just press F8 and select the usb. or f2/del, go to bootmenu. and select.
as for the digital license. make sure you do these first before you start/throw away your old hardware.
on your original PC, first link your license and machine to your account :
* press winkey+i. update & security. activation. add an account. sigin with your microsoft account.
* after all that is done you will see a message like "license linked to your account"
* you may or may not be asked to verify by your email to fully activate
on your new PC, transferring the digital license :
* press winkey+i. update & security. activation. troubleshoot. i changed hardware on this device recently.
* sign in with your account. go thru the following steps. passwords what-not.
* find the name of your new machine** and check "this is the device im using". activate.
** if you havent renamed it yet, it could be some random thing like DESKTOP-ASDF
done. ez pz!