This is the way. There is a GParted distro that you can boot from a USB-drive that will allow you to move the partition and expand it to take up the free space Windows left.
You should first install GParted to familiarise yourself a little with how the GUI looks. It’s relatively simple, definitely simpler than parted, but it doesn’t hurt to have a look around before doing it live.
It’s also good to note that everything you do in GParted needs to be applied before it’s actually done. You “cannot” accidentally delete a whole partition without actually hitting an apply button.